Cleveland Clinic Journal of Medicine

The role of diet in controlling symptoms of irritable bowel syndrome (IBS) has gained much traction over the years,¹ but until recently, diet therapy for IBS has been hindered by a lack of quality evidence, in part because of the challenges of conducting dietary clinical trials.

See related editorial

Several clinical trials have now been done that support a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) for managing IBS. Although restrictive and difficult to follow, the low-FODMAP diet is gaining popularity.

This article provides an overview of dietary interventions used to manage IBS, focusing on the low-FODMAP diet. We discuss mechanisms of malabsorption of FODMAPs and the role of FODMAPS in symptom induction; highlight clinical trials that provide evidence of benefits of the diet for IBS; and discuss the steps to implement it. We also address the nutritional adequacy of the diet and its potential effects on the gut microbiome.

IBS IS A COMMON FUNCTIONAL DISORDER

IBS is one of the most commonly diagnosed gastrointestinal disorders, and it has a significant impact on quality of life.² It is a functional disorder characterized by chronic abdominal pain and altered bowel habits in the absence of a structural or organic cause.

The Rome IV diagnostic criteria define IBS by the following: 

• Recurrent abdominal pain or discomfort at least 1 day a week in the last 3 months, associated with two or more of the following:
• Symptoms improved by defecation
• Onset associated with a change in frequency of stool
• Onset associated with a change in form or appearance of stool.

IBS mainly arises during young adulthood but can be diagnosed at any age.³

The pathophysiology of IBS involves mechanisms such as bowel distention, altered bowel motility, visceral hypersensitivity, and disruption of mucosal permeability.⁴ Several therapeutic modalities targeting these mechanisms have been implemented in IBS management, including antispasmodics, laxatives, antidepressants, antibiotics, and behavioral therapy. Diet is only one line of treatment and is most effective when part of a multipronged approach.

TRADITIONAL DIETARY MANAGEMENT

Diet is important in inducing the symptoms of IBS—and in controlling them. Patients identify eating as a common precipitator of symptoms, but the complex diet-symptom interaction is not fully understood and varies widely among patients. Traditional dietary advice for IBS includes adhering to a regular meal pattern, avoiding large meals, and reducing intake of fat, insoluble fibers, caffeine, spicy and gas-producing foods, and carbonated beverages.^5,6

Increase soluble fiber

Fiber and fiber supplements, particularly soluble fibers such as psyllium, calcium polycarbophil, and ispaghula husk are often recommended. A meta-analysis⁷ found that soluble fiber but not insoluble fiber (eg, wheat bran) is associated with an improvement in IBS symptoms (relative risk [RR] 0.84, 95% confidence interval [CI] 0.73–0.94). By improving stool consistency and accelerating transit, soluble fiber is especially useful in constipation-predominant IBS while posing a low risk for adverse outcomes.⁷ Fiber should be started at a low dose and gradually increased over several weeks to as much as 20 to 30 g/day.

Avoid wheat

Only about 4% of patients with IBS also have celiac disease, but estimating the prevalence of nonceliac gluten sensitivity is confounded by overlapping symptoms. There is some evidence implicating gluten in IBS: celiac disease and IBS overlap in their symptoms, and symptoms are often precipitated by gluten-containing foods in patients with IBS.⁸ The pathogenesis of gluten-induced (or wheat-induced) symptoms in IBS is unclear, and studies have had conflicting results as to the benefits of gluten restriction in IBS.⁹

In a study of patients with IBS whose symptoms improved when they started a gluten-free and low-FODMAP diet, symptoms did not return when gluten was reintroduced, suggesting that it is the fructan (a FODMAP) component of wheat rather than gluten that contributes to symptoms in IBS.¹⁰

Probiotics

Probiotics are increasingly being recommended as dietary supplements for people with IBS, as awareness increases of  the importance of the gut microbiota. In addition to their effects on the gut microbiota, probiotics in IBS have been shown to have anti-inflammatory effects, to alter gut motility, to modulate visceral hypersensitivity, and to restore epithelial integrity.

In a meta-analysis, Ford et al¹¹ found that probiotics improved global IBS symptoms more than placebo (RR 0.79, 95% CI 0.70–0.89) and also reduced abdominal pain, bloating, and flatulence scores.

Which species and strains are most beneficial and the optimal dosing and duration of treatment are still unclear. Data from studies of prebiotics (nutrients that encourage the growth of probiotic bacteria) and synbiotics (combinations of prebiotics and probiotics) are limited and insufficient to draw conclusions.

FODMAPS ARE SHORT-CHAIN CARBOHYDRATES

The term FODMAPs was initially coined by researchers at Monash University in Australia to describe  a collection of poorly absorbed short-chain fermentable carbohydrates that are natural components of many foods:

• Oligosaccharides, including fructans (which include inulins) and galacto-oligosaccharides
• Disaccharides, including lactose and sucrose
• Monosaccharides, including fructose
• Polyols, including sorbitol and mannitol.¹²

Intake of FODMAPs, especially fructose, has increased in Western diets over the past several decades from increased consumption of fruits and concentrated fruit juices, as well as from the widespread use of high-fructose corn syrup in processed foods and beverages.¹³

FODMAPs ARE POORLY ABSORBED

Different FODMAPs can be poorly absorbed for different reasons (Table 1). The poor absorption is related either to reduced or absent digestive enzymes (ie, hydrolases) or to slow transport across the intestinal mucosa. Excess FODMAPs in the distal small intestine and proximal colon exert osmotic pressure, drawing more water into the lumen. FODMAPs are also rapidly fermented by colonic bacteria, producing gas, bowel distention, and altered motility, all of which induce IBS symptoms.¹⁴

Fructans are fructose polymers that are not absorbed in human intestines. They have no intestinal hydrolases and no mechanisms for direct transport across the epithelium. However, a negligible amount may be absorbed after being degraded by microbes in the gut.¹⁵ Most dietary fructans are obtained from wheat and onion, which are actually low in fructans but tend to be consumed in large quantities.¹⁶

Galacto-oligosaccharides are available for colonic fermentation after ingestion due to lack of a human alpha-galactosidase. Common sources of galacto-oligosaccharides include legumes, nuts, seeds, some grains, dairy products, human milk, and some commercially produced forms added to infant formula.^17,18

Lactose is poorly absorbed in people with lactase deficiency. It is mainly present in dairy products but is also added to commercial foods, including breads, cakes, and some diet products.¹⁹

Fructose is the most abundant FODMAP in the Western diet. It is either present as a free sugar or generated from the digestive breakdown of sucrose. In the intestine, it is absorbed via a direct low-capacity glucose transporter (GLUT)-5 and through GLUT-2, which is more efficient but requires the coexistence of glucose. Because of this requirement, fructose is more likely to be malabsorbed when present in excess of glucose, as in people with diminished sucrase activity. The main sources of fructose in the Western diet are fruits and fruit products, honey, and foods with added high-fructose sweeteners.¹³

Polyols such as sorbitol and mannitol are absorbed by slow passive diffusion because they have no active intestinal transport system. They are found in fruits and vegetables. Sugar-free chewing gum is a particularly rich source of sorbitol.²⁰

QUANTIFYING FODMAP CONTENT

As interest in the low-FODMAP diet grew, studies were conducted to quantify FODMAPs in foods. One study used high-performance liquid chromatography to analyze FODMAP content in foods,²¹ and another evaluated fructan levels in a variety of fruits and vegetables using enzymatic hydrolysis.²² The Monash University low-FODMAP diet smartphone application provides patients and healthcare providers easy access to updated and detailed food analyses.²³

Table 2 lists foods high in FODMAPs along with low-FODMAP alternatives. Total FODMAP intake is important, as the effects are additive.²⁴ Readers and patients can be directed to the following websites for more information on the low-FODMAP diet: www.med.monash.edu/cecs/gastro/fodmap or www.ibsfree.net/what-is-fodmap-diet.

LOW-FODMAP DIET REDUCES SYMPTOMS

The low-FODMAP diet was inspired by the results of several studies that evaluated the role of dietary carbohydrates in inducing IBS symptoms and found improvement with their restriction.^25,26

One study found that 74% of patients with IBS had less bloating, nausea, abdominal pain, and diarrhea when they restricted their intake of fructose and fructans.²⁷

A prospective trial randomized 41 patients with IBS to 4 weeks of either a low-FODMAP diet or their habitual diet.²⁸ The low-FODMAP diet resulted in greater improvement in overall IBS symptoms (P < .05) and stool frequency (P = .008). This study was limited by different habitual diets between patients and by lack of standardization of the low-FODMAP diet.

Halmos et al,²⁹ in a randomized crossover trial, compared gastrointestinal symptoms in IBS patients over 3 weeks on a low-FODMAP diet vs a moderate-FODMAP (ie, regular) diet, as well as in healthy controls. Food was provided by the study and was matched for all nutrients. Up to 70% of the IBS patients had significantly lower overall symptom scores while on a low-FODMAP diet vs IBS patients on a regular diet (P < .001); bloating, abdominal pain, and flatulence were reduced. Symptoms were minimal and unaffected by either diet in the healthy controls.

A double-blind trial³⁰ randomly assigned 25 patients with IBS who initially responded to a low-FODMAP diet to be challenged by a graduated dose of fructose alone, fructans alone, a combination of both, or glucose. The severity of overall and individual symptoms was markedly more reduced with glucose consumption than with the other carbohydrates: 70% of patients receiving fructose, 77% of those receiving fructans, and 79% of those receiving a mixture of both reported that their symptoms were not adequately controlled, compared with 14% of patients receiving glucose (P ≤ .002).³⁰

Murray et al³¹ evaluated the gastrointestinal tract after a carbohydrate challenge consisting of 0.5 L of water containing 40 g of glucose, fructose, or inulin or a combination of 40 g of glucose and 40 g of fructose in 16 healthy volunteers. Magnetic resonance imaging was performed hourly for 5 hours to assess the volume of gastric contents, small-bowel water content, and colonic gas. Breath hydrogen was also measured, and symptoms were recorded after each imaging session.

Fructose significantly increased small-bowel water content compared with glucose (mean difference 28 L/min, P < .001), but combined glucose and fructose lessened the effect. Inulin had no significant effect on small-bowel water content (mean difference with glucose 2 L/min, P > .7) but led to the greatest production of colonic gas compared with glucose alone (mean difference 15 L/min, P < .05) and combined glucose and fructose (mean difference 12 L/min, P < .05). Inulin also produced the most breath hydrogen: 81% of participants had a rise after drinking inulin compared with 50% after drinking fructose. Glucose did not affect breath hydrogen concentrations, and combined glucose and fructose significantly reduced the concentration measured vs fructose alone. In patients who reported “gas” symptoms, a correlation was observed between the volume of gas in the colon and gas symptoms (r = 0.59, P < .0001).³¹

The authors concluded³¹ that long-chain carbohydrates such as inulin have a greater effect on colonic gas production and little effect on small-bowel water content, whereas small-chain FODMAPs such as fructose are likely to cause luminal distention in both the small and large intestines. The study also showed that combining equal amounts of glucose and fructose reduces malabsorption of fructose in the small bowel and reduces the effect of fructose on small-bowel water content and breath hydrogen concentration.³¹

PROBIOTICS HELP

A Danish study³² randomized 123 patients with IBS to one of three treatments: a low-FODMAP diet, a normal diet with probiotics containing the strain Lactobacillus rhamnosus GG (two capsules daily), or no special intervention. Symptoms were recorded weekly. IBS severity scores at week 6 were lower in patients on either the low-FODMAP diet or probiotics compared with the control group (P < .01). Subgroup analysis determined that patients with primarily diarrheal symptoms were more likely to have improved quality of life with the low-FODMAP diet.

A LOW-FODMAP DIET MAY ALSO HELP IN INFLAMMATORY BOWEL DISEASE

The low-FODMAP diet has also been studied in patients with inflammatory bowel disease with functional gut symptoms. In a retrospective pilot study,³³ overall symptoms improved in about half of such patients on a low-FODMAP diet. A controlled dietary intervention trial is needed to confirm these findings and define the role of the low-FODMAP approach for patients with inflammatory bowel disease.

Marsh et al³⁴ performed a meta-analysis of six randomized clinical trials and 16 nonrandomized interventions of a low-FODMAP diet on improving functional gastrointestinal symptoms in patients with either IBS or inflammatory bowel disease. They found significant improvements in:

• IBS Symptoms Severity Scores in the randomized trials (odds ratio [OR] 0.44, 95% CI 0.25–0.76)
• IBS Symptoms Severity Scores in the nonrandomized interventions (OR 0.03, 95% CI 0.01–0.2) 
• IBS Quality of Life scores in the randomized trials (OR 1.84, 95% CI 1.12–3.03)
• IBS Quality of Life scores in the nonrandomized interventions (OR 3.18, 95% CI 1.6–6.31)
• Overall symptom severity in the randomized trials (OR 1.81, 95% CI 1.11–2.95).

DIETARY COUNSELING IS RECOMMENDED

Adherence is a major factor in the success of the low-FODMAP diet in IBS management and is strongly correlated with improved symptoms.³⁵ Patients should be counseled on the role of food in inducing their symptoms. Haphazard dietary advice can be detrimental to outcomes, as many diets restrict food groups, impairing the consumption of essential nutrients.³⁶ The involvement of a knowledgeable dietitian is helpful, as physicians may lack sufficient training in dietary skills and knowledge of food composition.

Access to and cost of dietary counseling can be prohibitive for some patients. Group consultation, which can decrease costs to each patient, has been found to be as effective as one-on-one sessions when administering the low-FODMAP diet in functional bowel disorders.³⁷

ELIMINATION, THEN REINTRODUCTION

Before embarking on the low-FODMAP diet, the patient’s interest in making dietary changes should be explored, a dietary history taken, and unusual food choices or dietary behaviors assessed. The patient’s ability to adopt a restricted diet should also be gauged.

The diet should be implemented in two phases. The initial phase involves strict elimination of foods high in FODMAPs, usually over 6 to 8 weeks.³⁸ Symptom control should be assessed: failure to control symptoms requires assessment of adherence.

If symptoms are successfully controlled, then the second phase should begin with the aim of following a less-restricted version of the diet as tolerated. Foods should gradually be phased back in and symptoms monitored. This approach minimizes unnecessary dietary restriction and ensures that a maximum variety in the diet is achieved while maintaining adequate symptom control.³⁹

LOW-FODMAP DIET ALTERS THE GUT MICROBIOTA

Multiple putative benefits of certain bacterial species for colonic health have been reported, including the production of short-chain fatty acids. Colonic luminal concentrations of short-chain fatty acids may be important to gut health, given their role in intestinal secretion, absorption, motility, and epithelial cell structure. Because short-chain fatty acids are products of bacterial fermentation, a change in the delivery of fermentable substrates to the colon would be expected to alter the concentrations and output of fecal short-chain fatty acids.¹⁸

Several studies evaluated the effect of the low-FODMAP diet on intestinal microbiota, finding a change in the bacterial profile in the stool of patients who adopt this diet. Staudacher et al²⁸ found a marked reduction in luminal bifidobacteria concentration after 4 weeks of a low-FODMAP diet in patients with IBS.

A single-blind randomized crossover trial⁴⁰ investigated the effects of a low-FODMAP diet vs a carefully matched typical Australian diet in 27 patients with IBS and 6 healthy controls. Marked differences in absolute and relative bacterial abundance and diversity were found between the diets, but not in short-chain fatty acids or gut transit time. Compared with fecal microbiota on the typical diet, low FODMAP intake was associated with reduced absolute abundance of bacteria, and the typical FODMAP diet had evidence of stimulation of the growth of bacterial groups with putative health benefits.

The authors concluded⁴⁰ that the functional significance and health implications of such changes are reasons for caution when reducing FODMAP intake in the long term and recommended liberalizing FODMAP restriction to the level of adequate symptom control in IBS patients. The study also recommended that people without symptoms not go on the low-FODMAP diet.⁴⁰

Molecular approaches to characterize the gut microbiota are also being explored in an effort to identify its association with diet.

The sustainability of changes in gut microbiota and the potential long-term impact on health of following a low-FODMAP diet require further evaluation. In the meantime, patients following this diet should have FODMAP foods reintroduced based on tolerance and should consider taking probiotic supplements.⁴¹

DIETARY ADEQUACY OF THE LOW-FODMAP DIET

Continual dietary counseling should minimize nutritional inadequacies and ensure that FODMAPS are restricted only enough to control symptoms. Because no single food group is completely eliminated in this diet, patients are unlikely to experience inadequate nutrition.

Ledochowski et al²⁶ found that in the initial, strict phase of the diet, total intake of carbohydrates (eg, starches, sugars) was reduced but intake of total energy, protein, fat, and nonstarch polysaccharides was not affected. Calcium intake was reduced in those following a low-FODMAP diet for 4 weeks.

The diet can also reduce total fiber intake and subsequently worsen constipation-predominant IBS. For those patients, lightly fermented high-fiber alternatives like oat and rice bran can be used.

ACCUMULATING EVIDENCE

The low-FODMAP diet is accumulating quality evidence for its effectiveness in controlling the functional gastrointestinal symptoms in patients with IBS. It can be difficult to adhere to over the long term due to its restrictiveness, and it is important to gradually liberalize the diet while tailoring it to the individual patient and monitoring symptoms. Further clinical trials are needed to evaluate this diet in different IBS subtypes and other gastrointestinal disorders, while defining its nutritional adequacy and effects on the intestinal microbiota profile.

The role of diet in controlling symptoms of irritable bowel syndrome (IBS) has gained much traction over the years,¹ but until recently, diet therapy for IBS has been hindered by a lack of quality evidence, in part because of the challenges of conducting dietary clinical trials.

See related editorial

Several clinical trials have now been done that support a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) for managing IBS. Although restrictive and difficult to follow, the low-FODMAP diet is gaining popularity.

This article provides an overview of dietary interventions used to manage IBS, focusing on the low-FODMAP diet. We discuss mechanisms of malabsorption of FODMAPs and the role of FODMAPS in symptom induction; highlight clinical trials that provide evidence of benefits of the diet for IBS; and discuss the steps to implement it. We also address the nutritional adequacy of the diet and its potential effects on the gut microbiome.

IBS IS A COMMON FUNCTIONAL DISORDER

IBS is one of the most commonly diagnosed gastrointestinal disorders, and it has a significant impact on quality of life.² It is a functional disorder characterized by chronic abdominal pain and altered bowel habits in the absence of a structural or organic cause.

The Rome IV diagnostic criteria define IBS by the following: 

• Recurrent abdominal pain or discomfort at least 1 day a week in the last 3 months, associated with two or more of the following:
• Symptoms improved by defecation
• Onset associated with a change in frequency of stool
• Onset associated with a change in form or appearance of stool.

IBS mainly arises during young adulthood but can be diagnosed at any age.³

The pathophysiology of IBS involves mechanisms such as bowel distention, altered bowel motility, visceral hypersensitivity, and disruption of mucosal permeability.⁴ Several therapeutic modalities targeting these mechanisms have been implemented in IBS management, including antispasmodics, laxatives, antidepressants, antibiotics, and behavioral therapy. Diet is only one line of treatment and is most effective when part of a multipronged approach.

TRADITIONAL DIETARY MANAGEMENT

Diet is important in inducing the symptoms of IBS—and in controlling them. Patients identify eating as a common precipitator of symptoms, but the complex diet-symptom interaction is not fully understood and varies widely among patients. Traditional dietary advice for IBS includes adhering to a regular meal pattern, avoiding large meals, and reducing intake of fat, insoluble fibers, caffeine, spicy and gas-producing foods, and carbonated beverages.^5,6

Increase soluble fiber

Fiber and fiber supplements, particularly soluble fibers such as psyllium, calcium polycarbophil, and ispaghula husk are often recommended. A meta-analysis⁷ found that soluble fiber but not insoluble fiber (eg, wheat bran) is associated with an improvement in IBS symptoms (relative risk [RR] 0.84, 95% confidence interval [CI] 0.73–0.94). By improving stool consistency and accelerating transit, soluble fiber is especially useful in constipation-predominant IBS while posing a low risk for adverse outcomes.⁷ Fiber should be started at a low dose and gradually increased over several weeks to as much as 20 to 30 g/day.

Avoid wheat

Only about 4% of patients with IBS also have celiac disease, but estimating the prevalence of nonceliac gluten sensitivity is confounded by overlapping symptoms. There is some evidence implicating gluten in IBS: celiac disease and IBS overlap in their symptoms, and symptoms are often precipitated by gluten-containing foods in patients with IBS.⁸ The pathogenesis of gluten-induced (or wheat-induced) symptoms in IBS is unclear, and studies have had conflicting results as to the benefits of gluten restriction in IBS.⁹

In a study of patients with IBS whose symptoms improved when they started a gluten-free and low-FODMAP diet, symptoms did not return when gluten was reintroduced, suggesting that it is the fructan (a FODMAP) component of wheat rather than gluten that contributes to symptoms in IBS.¹⁰

Probiotics

Probiotics are increasingly being recommended as dietary supplements for people with IBS, as awareness increases of  the importance of the gut microbiota. In addition to their effects on the gut microbiota, probiotics in IBS have been shown to have anti-inflammatory effects, to alter gut motility, to modulate visceral hypersensitivity, and to restore epithelial integrity.

In a meta-analysis, Ford et al¹¹ found that probiotics improved global IBS symptoms more than placebo (RR 0.79, 95% CI 0.70–0.89) and also reduced abdominal pain, bloating, and flatulence scores.

Which species and strains are most beneficial and the optimal dosing and duration of treatment are still unclear. Data from studies of prebiotics (nutrients that encourage the growth of probiotic bacteria) and synbiotics (combinations of prebiotics and probiotics) are limited and insufficient to draw conclusions.

FODMAPS ARE SHORT-CHAIN CARBOHYDRATES

The term FODMAPs was initially coined by researchers at Monash University in Australia to describe  a collection of poorly absorbed short-chain fermentable carbohydrates that are natural components of many foods:

• Oligosaccharides, including fructans (which include inulins) and galacto-oligosaccharides
• Disaccharides, including lactose and sucrose
• Monosaccharides, including fructose
• Polyols, including sorbitol and mannitol.¹²

Intake of FODMAPs, especially fructose, has increased in Western diets over the past several decades from increased consumption of fruits and concentrated fruit juices, as well as from the widespread use of high-fructose corn syrup in processed foods and beverages.¹³

FODMAPs ARE POORLY ABSORBED

Different FODMAPs can be poorly absorbed for different reasons (Table 1). The poor absorption is related either to reduced or absent digestive enzymes (ie, hydrolases) or to slow transport across the intestinal mucosa. Excess FODMAPs in the distal small intestine and proximal colon exert osmotic pressure, drawing more water into the lumen. FODMAPs are also rapidly fermented by colonic bacteria, producing gas, bowel distention, and altered motility, all of which induce IBS symptoms.¹⁴

Fructans are fructose polymers that are not absorbed in human intestines. They have no intestinal hydrolases and no mechanisms for direct transport across the epithelium. However, a negligible amount may be absorbed after being degraded by microbes in the gut.¹⁵ Most dietary fructans are obtained from wheat and onion, which are actually low in fructans but tend to be consumed in large quantities.¹⁶

Galacto-oligosaccharides are available for colonic fermentation after ingestion due to lack of a human alpha-galactosidase. Common sources of galacto-oligosaccharides include legumes, nuts, seeds, some grains, dairy products, human milk, and some commercially produced forms added to infant formula.^17,18

Lactose is poorly absorbed in people with lactase deficiency. It is mainly present in dairy products but is also added to commercial foods, including breads, cakes, and some diet products.¹⁹

Fructose is the most abundant FODMAP in the Western diet. It is either present as a free sugar or generated from the digestive breakdown of sucrose. In the intestine, it is absorbed via a direct low-capacity glucose transporter (GLUT)-5 and through GLUT-2, which is more efficient but requires the coexistence of glucose. Because of this requirement, fructose is more likely to be malabsorbed when present in excess of glucose, as in people with diminished sucrase activity. The main sources of fructose in the Western diet are fruits and fruit products, honey, and foods with added high-fructose sweeteners.¹³

Polyols such as sorbitol and mannitol are absorbed by slow passive diffusion because they have no active intestinal transport system. They are found in fruits and vegetables. Sugar-free chewing gum is a particularly rich source of sorbitol.²⁰

QUANTIFYING FODMAP CONTENT

As interest in the low-FODMAP diet grew, studies were conducted to quantify FODMAPs in foods. One study used high-performance liquid chromatography to analyze FODMAP content in foods,²¹ and another evaluated fructan levels in a variety of fruits and vegetables using enzymatic hydrolysis.²² The Monash University low-FODMAP diet smartphone application provides patients and healthcare providers easy access to updated and detailed food analyses.²³

Table 2 lists foods high in FODMAPs along with low-FODMAP alternatives. Total FODMAP intake is important, as the effects are additive.²⁴ Readers and patients can be directed to the following websites for more information on the low-FODMAP diet: www.med.monash.edu/cecs/gastro/fodmap or www.ibsfree.net/what-is-fodmap-diet.

LOW-FODMAP DIET REDUCES SYMPTOMS

The low-FODMAP diet was inspired by the results of several studies that evaluated the role of dietary carbohydrates in inducing IBS symptoms and found improvement with their restriction.^25,26

One study found that 74% of patients with IBS had less bloating, nausea, abdominal pain, and diarrhea when they restricted their intake of fructose and fructans.²⁷

A prospective trial randomized 41 patients with IBS to 4 weeks of either a low-FODMAP diet or their habitual diet.²⁸ The low-FODMAP diet resulted in greater improvement in overall IBS symptoms (P < .05) and stool frequency (P = .008). This study was limited by different habitual diets between patients and by lack of standardization of the low-FODMAP diet.

Halmos et al,²⁹ in a randomized crossover trial, compared gastrointestinal symptoms in IBS patients over 3 weeks on a low-FODMAP diet vs a moderate-FODMAP (ie, regular) diet, as well as in healthy controls. Food was provided by the study and was matched for all nutrients. Up to 70% of the IBS patients had significantly lower overall symptom scores while on a low-FODMAP diet vs IBS patients on a regular diet (P < .001); bloating, abdominal pain, and flatulence were reduced. Symptoms were minimal and unaffected by either diet in the healthy controls.

A double-blind trial³⁰ randomly assigned 25 patients with IBS who initially responded to a low-FODMAP diet to be challenged by a graduated dose of fructose alone, fructans alone, a combination of both, or glucose. The severity of overall and individual symptoms was markedly more reduced with glucose consumption than with the other carbohydrates: 70% of patients receiving fructose, 77% of those receiving fructans, and 79% of those receiving a mixture of both reported that their symptoms were not adequately controlled, compared with 14% of patients receiving glucose (P ≤ .002).³⁰

Murray et al³¹ evaluated the gastrointestinal tract after a carbohydrate challenge consisting of 0.5 L of water containing 40 g of glucose, fructose, or inulin or a combination of 40 g of glucose and 40 g of fructose in 16 healthy volunteers. Magnetic resonance imaging was performed hourly for 5 hours to assess the volume of gastric contents, small-bowel water content, and colonic gas. Breath hydrogen was also measured, and symptoms were recorded after each imaging session.

Fructose significantly increased small-bowel water content compared with glucose (mean difference 28 L/min, P < .001), but combined glucose and fructose lessened the effect. Inulin had no significant effect on small-bowel water content (mean difference with glucose 2 L/min, P > .7) but led to the greatest production of colonic gas compared with glucose alone (mean difference 15 L/min, P < .05) and combined glucose and fructose (mean difference 12 L/min, P < .05). Inulin also produced the most breath hydrogen: 81% of participants had a rise after drinking inulin compared with 50% after drinking fructose. Glucose did not affect breath hydrogen concentrations, and combined glucose and fructose significantly reduced the concentration measured vs fructose alone. In patients who reported “gas” symptoms, a correlation was observed between the volume of gas in the colon and gas symptoms (r = 0.59, P < .0001).³¹

The authors concluded³¹ that long-chain carbohydrates such as inulin have a greater effect on colonic gas production and little effect on small-bowel water content, whereas small-chain FODMAPs such as fructose are likely to cause luminal distention in both the small and large intestines. The study also showed that combining equal amounts of glucose and fructose reduces malabsorption of fructose in the small bowel and reduces the effect of fructose on small-bowel water content and breath hydrogen concentration.³¹

PROBIOTICS HELP

A Danish study³² randomized 123 patients with IBS to one of three treatments: a low-FODMAP diet, a normal diet with probiotics containing the strain Lactobacillus rhamnosus GG (two capsules daily), or no special intervention. Symptoms were recorded weekly. IBS severity scores at week 6 were lower in patients on either the low-FODMAP diet or probiotics compared with the control group (P < .01). Subgroup analysis determined that patients with primarily diarrheal symptoms were more likely to have improved quality of life with the low-FODMAP diet.

A LOW-FODMAP DIET MAY ALSO HELP IN INFLAMMATORY BOWEL DISEASE

The low-FODMAP diet has also been studied in patients with inflammatory bowel disease with functional gut symptoms. In a retrospective pilot study,³³ overall symptoms improved in about half of such patients on a low-FODMAP diet. A controlled dietary intervention trial is needed to confirm these findings and define the role of the low-FODMAP approach for patients with inflammatory bowel disease.

Marsh et al³⁴ performed a meta-analysis of six randomized clinical trials and 16 nonrandomized interventions of a low-FODMAP diet on improving functional gastrointestinal symptoms in patients with either IBS or inflammatory bowel disease. They found significant improvements in:

• IBS Symptoms Severity Scores in the randomized trials (odds ratio [OR] 0.44, 95% CI 0.25–0.76)
• IBS Symptoms Severity Scores in the nonrandomized interventions (OR 0.03, 95% CI 0.01–0.2) 
• IBS Quality of Life scores in the randomized trials (OR 1.84, 95% CI 1.12–3.03)
• IBS Quality of Life scores in the nonrandomized interventions (OR 3.18, 95% CI 1.6–6.31)
• Overall symptom severity in the randomized trials (OR 1.81, 95% CI 1.11–2.95).

DIETARY COUNSELING IS RECOMMENDED

Adherence is a major factor in the success of the low-FODMAP diet in IBS management and is strongly correlated with improved symptoms.³⁵ Patients should be counseled on the role of food in inducing their symptoms. Haphazard dietary advice can be detrimental to outcomes, as many diets restrict food groups, impairing the consumption of essential nutrients.³⁶ The involvement of a knowledgeable dietitian is helpful, as physicians may lack sufficient training in dietary skills and knowledge of food composition.

Access to and cost of dietary counseling can be prohibitive for some patients. Group consultation, which can decrease costs to each patient, has been found to be as effective as one-on-one sessions when administering the low-FODMAP diet in functional bowel disorders.³⁷

ELIMINATION, THEN REINTRODUCTION

Before embarking on the low-FODMAP diet, the patient’s interest in making dietary changes should be explored, a dietary history taken, and unusual food choices or dietary behaviors assessed. The patient’s ability to adopt a restricted diet should also be gauged.

The diet should be implemented in two phases. The initial phase involves strict elimination of foods high in FODMAPs, usually over 6 to 8 weeks.³⁸ Symptom control should be assessed: failure to control symptoms requires assessment of adherence.

If symptoms are successfully controlled, then the second phase should begin with the aim of following a less-restricted version of the diet as tolerated. Foods should gradually be phased back in and symptoms monitored. This approach minimizes unnecessary dietary restriction and ensures that a maximum variety in the diet is achieved while maintaining adequate symptom control.³⁹

LOW-FODMAP DIET ALTERS THE GUT MICROBIOTA

Multiple putative benefits of certain bacterial species for colonic health have been reported, including the production of short-chain fatty acids. Colonic luminal concentrations of short-chain fatty acids may be important to gut health, given their role in intestinal secretion, absorption, motility, and epithelial cell structure. Because short-chain fatty acids are products of bacterial fermentation, a change in the delivery of fermentable substrates to the colon would be expected to alter the concentrations and output of fecal short-chain fatty acids.¹⁸

Several studies evaluated the effect of the low-FODMAP diet on intestinal microbiota, finding a change in the bacterial profile in the stool of patients who adopt this diet. Staudacher et al²⁸ found a marked reduction in luminal bifidobacteria concentration after 4 weeks of a low-FODMAP diet in patients with IBS.

A single-blind randomized crossover trial⁴⁰ investigated the effects of a low-FODMAP diet vs a carefully matched typical Australian diet in 27 patients with IBS and 6 healthy controls. Marked differences in absolute and relative bacterial abundance and diversity were found between the diets, but not in short-chain fatty acids or gut transit time. Compared with fecal microbiota on the typical diet, low FODMAP intake was associated with reduced absolute abundance of bacteria, and the typical FODMAP diet had evidence of stimulation of the growth of bacterial groups with putative health benefits.

The authors concluded⁴⁰ that the functional significance and health implications of such changes are reasons for caution when reducing FODMAP intake in the long term and recommended liberalizing FODMAP restriction to the level of adequate symptom control in IBS patients. The study also recommended that people without symptoms not go on the low-FODMAP diet.⁴⁰

Molecular approaches to characterize the gut microbiota are also being explored in an effort to identify its association with diet.

The sustainability of changes in gut microbiota and the potential long-term impact on health of following a low-FODMAP diet require further evaluation. In the meantime, patients following this diet should have FODMAP foods reintroduced based on tolerance and should consider taking probiotic supplements.⁴¹

DIETARY ADEQUACY OF THE LOW-FODMAP DIET

Continual dietary counseling should minimize nutritional inadequacies and ensure that FODMAPS are restricted only enough to control symptoms. Because no single food group is completely eliminated in this diet, patients are unlikely to experience inadequate nutrition.

Ledochowski et al²⁶ found that in the initial, strict phase of the diet, total intake of carbohydrates (eg, starches, sugars) was reduced but intake of total energy, protein, fat, and nonstarch polysaccharides was not affected. Calcium intake was reduced in those following a low-FODMAP diet for 4 weeks.

The diet can also reduce total fiber intake and subsequently worsen constipation-predominant IBS. For those patients, lightly fermented high-fiber alternatives like oat and rice bran can be used.

ACCUMULATING EVIDENCE

The low-FODMAP diet is accumulating quality evidence for its effectiveness in controlling the functional gastrointestinal symptoms in patients with IBS. It can be difficult to adhere to over the long term due to its restrictiveness, and it is important to gradually liberalize the diet while tailoring it to the individual patient and monitoring symptoms. Further clinical trials are needed to evaluate this diet in different IBS subtypes and other gastrointestinal disorders, while defining its nutritional adequacy and effects on the intestinal microbiota profile.

The role of diet in controlling symptoms of irritable bowel syndrome (IBS) has gained much traction over the years,¹ but until recently, diet therapy for IBS has been hindered by a lack of quality evidence, in part because of the challenges of conducting dietary clinical trials.

See related editorial

Several clinical trials have now been done that support a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) for managing IBS. Although restrictive and difficult to follow, the low-FODMAP diet is gaining popularity.

This article provides an overview of dietary interventions used to manage IBS, focusing on the low-FODMAP diet. We discuss mechanisms of malabsorption of FODMAPs and the role of FODMAPS in symptom induction; highlight clinical trials that provide evidence of benefits of the diet for IBS; and discuss the steps to implement it. We also address the nutritional adequacy of the diet and its potential effects on the gut microbiome.

IBS IS A COMMON FUNCTIONAL DISORDER

IBS is one of the most commonly diagnosed gastrointestinal disorders, and it has a significant impact on quality of life.² It is a functional disorder characterized by chronic abdominal pain and altered bowel habits in the absence of a structural or organic cause.

The Rome IV diagnostic criteria define IBS by the following: 

• Recurrent abdominal pain or discomfort at least 1 day a week in the last 3 months, associated with two or more of the following:
• Symptoms improved by defecation
• Onset associated with a change in frequency of stool
• Onset associated with a change in form or appearance of stool.

IBS mainly arises during young adulthood but can be diagnosed at any age.³

The pathophysiology of IBS involves mechanisms such as bowel distention, altered bowel motility, visceral hypersensitivity, and disruption of mucosal permeability.⁴ Several therapeutic modalities targeting these mechanisms have been implemented in IBS management, including antispasmodics, laxatives, antidepressants, antibiotics, and behavioral therapy. Diet is only one line of treatment and is most effective when part of a multipronged approach.

TRADITIONAL DIETARY MANAGEMENT

Diet is important in inducing the symptoms of IBS—and in controlling them. Patients identify eating as a common precipitator of symptoms, but the complex diet-symptom interaction is not fully understood and varies widely among patients. Traditional dietary advice for IBS includes adhering to a regular meal pattern, avoiding large meals, and reducing intake of fat, insoluble fibers, caffeine, spicy and gas-producing foods, and carbonated beverages.^5,6

Increase soluble fiber

Fiber and fiber supplements, particularly soluble fibers such as psyllium, calcium polycarbophil, and ispaghula husk are often recommended. A meta-analysis⁷ found that soluble fiber but not insoluble fiber (eg, wheat bran) is associated with an improvement in IBS symptoms (relative risk [RR] 0.84, 95% confidence interval [CI] 0.73–0.94). By improving stool consistency and accelerating transit, soluble fiber is especially useful in constipation-predominant IBS while posing a low risk for adverse outcomes.⁷ Fiber should be started at a low dose and gradually increased over several weeks to as much as 20 to 30 g/day.

Avoid wheat

Only about 4% of patients with IBS also have celiac disease, but estimating the prevalence of nonceliac gluten sensitivity is confounded by overlapping symptoms. There is some evidence implicating gluten in IBS: celiac disease and IBS overlap in their symptoms, and symptoms are often precipitated by gluten-containing foods in patients with IBS.⁸ The pathogenesis of gluten-induced (or wheat-induced) symptoms in IBS is unclear, and studies have had conflicting results as to the benefits of gluten restriction in IBS.⁹

In a study of patients with IBS whose symptoms improved when they started a gluten-free and low-FODMAP diet, symptoms did not return when gluten was reintroduced, suggesting that it is the fructan (a FODMAP) component of wheat rather than gluten that contributes to symptoms in IBS.¹⁰

Probiotics

Probiotics are increasingly being recommended as dietary supplements for people with IBS, as awareness increases of  the importance of the gut microbiota. In addition to their effects on the gut microbiota, probiotics in IBS have been shown to have anti-inflammatory effects, to alter gut motility, to modulate visceral hypersensitivity, and to restore epithelial integrity.

In a meta-analysis, Ford et al¹¹ found that probiotics improved global IBS symptoms more than placebo (RR 0.79, 95% CI 0.70–0.89) and also reduced abdominal pain, bloating, and flatulence scores.

Which species and strains are most beneficial and the optimal dosing and duration of treatment are still unclear. Data from studies of prebiotics (nutrients that encourage the growth of probiotic bacteria) and synbiotics (combinations of prebiotics and probiotics) are limited and insufficient to draw conclusions.

FODMAPS ARE SHORT-CHAIN CARBOHYDRATES

The term FODMAPs was initially coined by researchers at Monash University in Australia to describe  a collection of poorly absorbed short-chain fermentable carbohydrates that are natural components of many foods:

• Oligosaccharides, including fructans (which include inulins) and galacto-oligosaccharides
• Disaccharides, including lactose and sucrose
• Monosaccharides, including fructose
• Polyols, including sorbitol and mannitol.¹²

Intake of FODMAPs, especially fructose, has increased in Western diets over the past several decades from increased consumption of fruits and concentrated fruit juices, as well as from the widespread use of high-fructose corn syrup in processed foods and beverages.¹³

FODMAPs ARE POORLY ABSORBED

Different FODMAPs can be poorly absorbed for different reasons (Table 1). The poor absorption is related either to reduced or absent digestive enzymes (ie, hydrolases) or to slow transport across the intestinal mucosa. Excess FODMAPs in the distal small intestine and proximal colon exert osmotic pressure, drawing more water into the lumen. FODMAPs are also rapidly fermented by colonic bacteria, producing gas, bowel distention, and altered motility, all of which induce IBS symptoms.¹⁴

Fructans are fructose polymers that are not absorbed in human intestines. They have no intestinal hydrolases and no mechanisms for direct transport across the epithelium. However, a negligible amount may be absorbed after being degraded by microbes in the gut.¹⁵ Most dietary fructans are obtained from wheat and onion, which are actually low in fructans but tend to be consumed in large quantities.¹⁶

Galacto-oligosaccharides are available for colonic fermentation after ingestion due to lack of a human alpha-galactosidase. Common sources of galacto-oligosaccharides include legumes, nuts, seeds, some grains, dairy products, human milk, and some commercially produced forms added to infant formula.^17,18

Lactose is poorly absorbed in people with lactase deficiency. It is mainly present in dairy products but is also added to commercial foods, including breads, cakes, and some diet products.¹⁹

Fructose is the most abundant FODMAP in the Western diet. It is either present as a free sugar or generated from the digestive breakdown of sucrose. In the intestine, it is absorbed via a direct low-capacity glucose transporter (GLUT)-5 and through GLUT-2, which is more efficient but requires the coexistence of glucose. Because of this requirement, fructose is more likely to be malabsorbed when present in excess of glucose, as in people with diminished sucrase activity. The main sources of fructose in the Western diet are fruits and fruit products, honey, and foods with added high-fructose sweeteners.¹³

Polyols such as sorbitol and mannitol are absorbed by slow passive diffusion because they have no active intestinal transport system. They are found in fruits and vegetables. Sugar-free chewing gum is a particularly rich source of sorbitol.²⁰

QUANTIFYING FODMAP CONTENT

As interest in the low-FODMAP diet grew, studies were conducted to quantify FODMAPs in foods. One study used high-performance liquid chromatography to analyze FODMAP content in foods,²¹ and another evaluated fructan levels in a variety of fruits and vegetables using enzymatic hydrolysis.²² The Monash University low-FODMAP diet smartphone application provides patients and healthcare providers easy access to updated and detailed food analyses.²³

Table 2 lists foods high in FODMAPs along with low-FODMAP alternatives. Total FODMAP intake is important, as the effects are additive.²⁴ Readers and patients can be directed to the following websites for more information on the low-FODMAP diet: www.med.monash.edu/cecs/gastro/fodmap or www.ibsfree.net/what-is-fodmap-diet.

LOW-FODMAP DIET REDUCES SYMPTOMS

The low-FODMAP diet was inspired by the results of several studies that evaluated the role of dietary carbohydrates in inducing IBS symptoms and found improvement with their restriction.^25,26

One study found that 74% of patients with IBS had less bloating, nausea, abdominal pain, and diarrhea when they restricted their intake of fructose and fructans.²⁷

A prospective trial randomized 41 patients with IBS to 4 weeks of either a low-FODMAP diet or their habitual diet.²⁸ The low-FODMAP diet resulted in greater improvement in overall IBS symptoms (P < .05) and stool frequency (P = .008). This study was limited by different habitual diets between patients and by lack of standardization of the low-FODMAP diet.

Halmos et al,²⁹ in a randomized crossover trial, compared gastrointestinal symptoms in IBS patients over 3 weeks on a low-FODMAP diet vs a moderate-FODMAP (ie, regular) diet, as well as in healthy controls. Food was provided by the study and was matched for all nutrients. Up to 70% of the IBS patients had significantly lower overall symptom scores while on a low-FODMAP diet vs IBS patients on a regular diet (P < .001); bloating, abdominal pain, and flatulence were reduced. Symptoms were minimal and unaffected by either diet in the healthy controls.

A double-blind trial³⁰ randomly assigned 25 patients with IBS who initially responded to a low-FODMAP diet to be challenged by a graduated dose of fructose alone, fructans alone, a combination of both, or glucose. The severity of overall and individual symptoms was markedly more reduced with glucose consumption than with the other carbohydrates: 70% of patients receiving fructose, 77% of those receiving fructans, and 79% of those receiving a mixture of both reported that their symptoms were not adequately controlled, compared with 14% of patients receiving glucose (P ≤ .002).³⁰

Murray et al³¹ evaluated the gastrointestinal tract after a carbohydrate challenge consisting of 0.5 L of water containing 40 g of glucose, fructose, or inulin or a combination of 40 g of glucose and 40 g of fructose in 16 healthy volunteers. Magnetic resonance imaging was performed hourly for 5 hours to assess the volume of gastric contents, small-bowel water content, and colonic gas. Breath hydrogen was also measured, and symptoms were recorded after each imaging session.

Fructose significantly increased small-bowel water content compared with glucose (mean difference 28 L/min, P < .001), but combined glucose and fructose lessened the effect. Inulin had no significant effect on small-bowel water content (mean difference with glucose 2 L/min, P > .7) but led to the greatest production of colonic gas compared with glucose alone (mean difference 15 L/min, P < .05) and combined glucose and fructose (mean difference 12 L/min, P < .05). Inulin also produced the most breath hydrogen: 81% of participants had a rise after drinking inulin compared with 50% after drinking fructose. Glucose did not affect breath hydrogen concentrations, and combined glucose and fructose significantly reduced the concentration measured vs fructose alone. In patients who reported “gas” symptoms, a correlation was observed between the volume of gas in the colon and gas symptoms (r = 0.59, P < .0001).³¹

The authors concluded³¹ that long-chain carbohydrates such as inulin have a greater effect on colonic gas production and little effect on small-bowel water content, whereas small-chain FODMAPs such as fructose are likely to cause luminal distention in both the small and large intestines. The study also showed that combining equal amounts of glucose and fructose reduces malabsorption of fructose in the small bowel and reduces the effect of fructose on small-bowel water content and breath hydrogen concentration.³¹

PROBIOTICS HELP

A Danish study³² randomized 123 patients with IBS to one of three treatments: a low-FODMAP diet, a normal diet with probiotics containing the strain Lactobacillus rhamnosus GG (two capsules daily), or no special intervention. Symptoms were recorded weekly. IBS severity scores at week 6 were lower in patients on either the low-FODMAP diet or probiotics compared with the control group (P < .01). Subgroup analysis determined that patients with primarily diarrheal symptoms were more likely to have improved quality of life with the low-FODMAP diet.

A LOW-FODMAP DIET MAY ALSO HELP IN INFLAMMATORY BOWEL DISEASE

The low-FODMAP diet has also been studied in patients with inflammatory bowel disease with functional gut symptoms. In a retrospective pilot study,³³ overall symptoms improved in about half of such patients on a low-FODMAP diet. A controlled dietary intervention trial is needed to confirm these findings and define the role of the low-FODMAP approach for patients with inflammatory bowel disease.

Marsh et al³⁴ performed a meta-analysis of six randomized clinical trials and 16 nonrandomized interventions of a low-FODMAP diet on improving functional gastrointestinal symptoms in patients with either IBS or inflammatory bowel disease. They found significant improvements in:

• IBS Symptoms Severity Scores in the randomized trials (odds ratio [OR] 0.44, 95% CI 0.25–0.76)
• IBS Symptoms Severity Scores in the nonrandomized interventions (OR 0.03, 95% CI 0.01–0.2) 
• IBS Quality of Life scores in the randomized trials (OR 1.84, 95% CI 1.12–3.03)
• IBS Quality of Life scores in the nonrandomized interventions (OR 3.18, 95% CI 1.6–6.31)
• Overall symptom severity in the randomized trials (OR 1.81, 95% CI 1.11–2.95).

DIETARY COUNSELING IS RECOMMENDED

Adherence is a major factor in the success of the low-FODMAP diet in IBS management and is strongly correlated with improved symptoms.³⁵ Patients should be counseled on the role of food in inducing their symptoms. Haphazard dietary advice can be detrimental to outcomes, as many diets restrict food groups, impairing the consumption of essential nutrients.³⁶ The involvement of a knowledgeable dietitian is helpful, as physicians may lack sufficient training in dietary skills and knowledge of food composition.

Access to and cost of dietary counseling can be prohibitive for some patients. Group consultation, which can decrease costs to each patient, has been found to be as effective as one-on-one sessions when administering the low-FODMAP diet in functional bowel disorders.³⁷

ELIMINATION, THEN REINTRODUCTION

Before embarking on the low-FODMAP diet, the patient’s interest in making dietary changes should be explored, a dietary history taken, and unusual food choices or dietary behaviors assessed. The patient’s ability to adopt a restricted diet should also be gauged.

The diet should be implemented in two phases. The initial phase involves strict elimination of foods high in FODMAPs, usually over 6 to 8 weeks.³⁸ Symptom control should be assessed: failure to control symptoms requires assessment of adherence.

If symptoms are successfully controlled, then the second phase should begin with the aim of following a less-restricted version of the diet as tolerated. Foods should gradually be phased back in and symptoms monitored. This approach minimizes unnecessary dietary restriction and ensures that a maximum variety in the diet is achieved while maintaining adequate symptom control.³⁹

LOW-FODMAP DIET ALTERS THE GUT MICROBIOTA

Multiple putative benefits of certain bacterial species for colonic health have been reported, including the production of short-chain fatty acids. Colonic luminal concentrations of short-chain fatty acids may be important to gut health, given their role in intestinal secretion, absorption, motility, and epithelial cell structure. Because short-chain fatty acids are products of bacterial fermentation, a change in the delivery of fermentable substrates to the colon would be expected to alter the concentrations and output of fecal short-chain fatty acids.¹⁸

Several studies evaluated the effect of the low-FODMAP diet on intestinal microbiota, finding a change in the bacterial profile in the stool of patients who adopt this diet. Staudacher et al²⁸ found a marked reduction in luminal bifidobacteria concentration after 4 weeks of a low-FODMAP diet in patients with IBS.

A single-blind randomized crossover trial⁴⁰ investigated the effects of a low-FODMAP diet vs a carefully matched typical Australian diet in 27 patients with IBS and 6 healthy controls. Marked differences in absolute and relative bacterial abundance and diversity were found between the diets, but not in short-chain fatty acids or gut transit time. Compared with fecal microbiota on the typical diet, low FODMAP intake was associated with reduced absolute abundance of bacteria, and the typical FODMAP diet had evidence of stimulation of the growth of bacterial groups with putative health benefits.

The authors concluded⁴⁰ that the functional significance and health implications of such changes are reasons for caution when reducing FODMAP intake in the long term and recommended liberalizing FODMAP restriction to the level of adequate symptom control in IBS patients. The study also recommended that people without symptoms not go on the low-FODMAP diet.⁴⁰

Molecular approaches to characterize the gut microbiota are also being explored in an effort to identify its association with diet.

The sustainability of changes in gut microbiota and the potential long-term impact on health of following a low-FODMAP diet require further evaluation. In the meantime, patients following this diet should have FODMAP foods reintroduced based on tolerance and should consider taking probiotic supplements.⁴¹

DIETARY ADEQUACY OF THE LOW-FODMAP DIET

Continual dietary counseling should minimize nutritional inadequacies and ensure that FODMAPS are restricted only enough to control symptoms. Because no single food group is completely eliminated in this diet, patients are unlikely to experience inadequate nutrition.

Ledochowski et al²⁶ found that in the initial, strict phase of the diet, total intake of carbohydrates (eg, starches, sugars) was reduced but intake of total energy, protein, fat, and nonstarch polysaccharides was not affected. Calcium intake was reduced in those following a low-FODMAP diet for 4 weeks.

The diet can also reduce total fiber intake and subsequently worsen constipation-predominant IBS. For those patients, lightly fermented high-fiber alternatives like oat and rice bran can be used.

ACCUMULATING EVIDENCE

The low-FODMAP diet is accumulating quality evidence for its effectiveness in controlling the functional gastrointestinal symptoms in patients with IBS. It can be difficult to adhere to over the long term due to its restrictiveness, and it is important to gradually liberalize the diet while tailoring it to the individual patient and monitoring symptoms. Further clinical trials are needed to evaluate this diet in different IBS subtypes and other gastrointestinal disorders, while defining its nutritional adequacy and effects on the intestinal microbiota profile.

Diet plays an important role in the pathophysiology of irritable bowel syndrome (IBS) and is an effective tool in managing this disorder. This includes a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs).

See related article

These indigestible and poorly absorbed short-chain carbohydrates trigger IBS symptoms and are thought to exert their effects by increasing osmotic pressure in the lumen of the intestine and by providing a substrate for bacterial fermentation with consequent gas production.¹ The gas causes abdominal distention, and the change in pressure in the lumen of the large intestine affects the release of serotonin, causing abdominal pain and discomfort.

THE MECHANISMS ARE COMPLICATED

Recent studies have shown that the mechanisms by which FODMAPs exert their effects are more complicated than originally thought.¹

All segments of the gastrointestinal tract contain endocrine cells scattered between the mucosal epithelial cells facing the intestinal lumen.^1,2 There are at least 10 types of endocrine cell, and they regulate gastrointestinal motility, secretion, absorption, visceral sensitivity, local immune defense, cell proliferation, and appetite.^2–4 Abnormal densities of gastrointestinal endocrine cells have been reported in patients with IBS, which may explain the dysmotility, visceral hypersensitivity, and abnormal intestinal secretion seen in these patients.⁵

But other factors such as diet, intestinal microbiota, genetics, and low-grade inflammation also play pivotal roles in the pathophysiology of IBS by exerting effects on gastrointestinal endocrine cells. The abnormalities in the gastrointestinal endocrine cells in IBS are thought to be brought about by aberrant differentiation of stem cells into endocrine cells (Figure 1).⁶

A diet low in FODMAPs appears to induce changes in the intestinal microbiota and gastrointestinal endocrine cells and to reduce IBS symptoms.⁶

GLUTEN IS IMPLICATED

Another dietary factor in IBS is gluten. Symptoms of IBS and celiac disease overlap: most studies have found that fewer than 5% of patients with celiac disease are misdiagnosed as having IBS based on the symptom criteria for IBS, but some studies report a rate as high as 32%.⁷ In addition, 38% of patients with celiac disease who consume a gluten-free diet fulfill the symptom-based Rome criteria for IBS.⁷

The contribution of gluten to IBS does not end with the coexistence of IBS and celiac disease, but also includes the newly debated diagnosis of nonceliac gluten sensitivity, characterized by gastrointestinal symptoms (abdominal pain, diarrhea, constipation, nausea, and vomiting) and other symptoms (headache, musculoskeletal pain, “brain fog,” fatigue, and depression) that are similar to those of IBS. Symptoms are triggered by the ingestion of wheat products, are improved after wheat products are removed from the diet, and relapse after a wheat challenge.⁷

Nonceliac gluten sensitivity is often perceivable by patients, resulting in self-diagnosis and self-treatment.⁴ However, it is not clear whether it is gluten or the fructans and galactans in wheat that are responsible for triggering their symptoms.⁷

DIETARY GUIDANCE IS NEEDED

A low-FODMAP diet with small amounts of insoluble dietary fiber improves symptoms and quality of life in patients with IBS, but dietary guidance is critical and should be personalized because patients differ in how they tolerate foods rich in FODMAPs, probably owing to differing intestinal microbiota among individuals.^3,8 Intake of probiotics increases tolerance of FODMAP-rich foods and should also be recommended.^3,8,9 Because of the rigorous restrictions of the low-FODMAP diet, patients who receive personalized guidance are more inclined to adhere to the diet and to avoid vitamin and mineral deficiencies.⁹

Diet plays an important role in the pathophysiology of irritable bowel syndrome (IBS) and is an effective tool in managing this disorder. This includes a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs).

See related article

These indigestible and poorly absorbed short-chain carbohydrates trigger IBS symptoms and are thought to exert their effects by increasing osmotic pressure in the lumen of the intestine and by providing a substrate for bacterial fermentation with consequent gas production.¹ The gas causes abdominal distention, and the change in pressure in the lumen of the large intestine affects the release of serotonin, causing abdominal pain and discomfort.

THE MECHANISMS ARE COMPLICATED

Recent studies have shown that the mechanisms by which FODMAPs exert their effects are more complicated than originally thought.¹

All segments of the gastrointestinal tract contain endocrine cells scattered between the mucosal epithelial cells facing the intestinal lumen.^1,2 There are at least 10 types of endocrine cell, and they regulate gastrointestinal motility, secretion, absorption, visceral sensitivity, local immune defense, cell proliferation, and appetite.^2–4 Abnormal densities of gastrointestinal endocrine cells have been reported in patients with IBS, which may explain the dysmotility, visceral hypersensitivity, and abnormal intestinal secretion seen in these patients.⁵

But other factors such as diet, intestinal microbiota, genetics, and low-grade inflammation also play pivotal roles in the pathophysiology of IBS by exerting effects on gastrointestinal endocrine cells. The abnormalities in the gastrointestinal endocrine cells in IBS are thought to be brought about by aberrant differentiation of stem cells into endocrine cells (Figure 1).⁶

A diet low in FODMAPs appears to induce changes in the intestinal microbiota and gastrointestinal endocrine cells and to reduce IBS symptoms.⁶

GLUTEN IS IMPLICATED

Another dietary factor in IBS is gluten. Symptoms of IBS and celiac disease overlap: most studies have found that fewer than 5% of patients with celiac disease are misdiagnosed as having IBS based on the symptom criteria for IBS, but some studies report a rate as high as 32%.⁷ In addition, 38% of patients with celiac disease who consume a gluten-free diet fulfill the symptom-based Rome criteria for IBS.⁷

The contribution of gluten to IBS does not end with the coexistence of IBS and celiac disease, but also includes the newly debated diagnosis of nonceliac gluten sensitivity, characterized by gastrointestinal symptoms (abdominal pain, diarrhea, constipation, nausea, and vomiting) and other symptoms (headache, musculoskeletal pain, “brain fog,” fatigue, and depression) that are similar to those of IBS. Symptoms are triggered by the ingestion of wheat products, are improved after wheat products are removed from the diet, and relapse after a wheat challenge.⁷

Nonceliac gluten sensitivity is often perceivable by patients, resulting in self-diagnosis and self-treatment.⁴ However, it is not clear whether it is gluten or the fructans and galactans in wheat that are responsible for triggering their symptoms.⁷

DIETARY GUIDANCE IS NEEDED

A low-FODMAP diet with small amounts of insoluble dietary fiber improves symptoms and quality of life in patients with IBS, but dietary guidance is critical and should be personalized because patients differ in how they tolerate foods rich in FODMAPs, probably owing to differing intestinal microbiota among individuals.^3,8 Intake of probiotics increases tolerance of FODMAP-rich foods and should also be recommended.^3,8,9 Because of the rigorous restrictions of the low-FODMAP diet, patients who receive personalized guidance are more inclined to adhere to the diet and to avoid vitamin and mineral deficiencies.⁹

Diet plays an important role in the pathophysiology of irritable bowel syndrome (IBS) and is an effective tool in managing this disorder. This includes a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs).

See related article

These indigestible and poorly absorbed short-chain carbohydrates trigger IBS symptoms and are thought to exert their effects by increasing osmotic pressure in the lumen of the intestine and by providing a substrate for bacterial fermentation with consequent gas production.¹ The gas causes abdominal distention, and the change in pressure in the lumen of the large intestine affects the release of serotonin, causing abdominal pain and discomfort.

THE MECHANISMS ARE COMPLICATED

Recent studies have shown that the mechanisms by which FODMAPs exert their effects are more complicated than originally thought.¹

All segments of the gastrointestinal tract contain endocrine cells scattered between the mucosal epithelial cells facing the intestinal lumen.^1,2 There are at least 10 types of endocrine cell, and they regulate gastrointestinal motility, secretion, absorption, visceral sensitivity, local immune defense, cell proliferation, and appetite.^2–4 Abnormal densities of gastrointestinal endocrine cells have been reported in patients with IBS, which may explain the dysmotility, visceral hypersensitivity, and abnormal intestinal secretion seen in these patients.⁵

But other factors such as diet, intestinal microbiota, genetics, and low-grade inflammation also play pivotal roles in the pathophysiology of IBS by exerting effects on gastrointestinal endocrine cells. The abnormalities in the gastrointestinal endocrine cells in IBS are thought to be brought about by aberrant differentiation of stem cells into endocrine cells (Figure 1).⁶

A diet low in FODMAPs appears to induce changes in the intestinal microbiota and gastrointestinal endocrine cells and to reduce IBS symptoms.⁶

GLUTEN IS IMPLICATED

Another dietary factor in IBS is gluten. Symptoms of IBS and celiac disease overlap: most studies have found that fewer than 5% of patients with celiac disease are misdiagnosed as having IBS based on the symptom criteria for IBS, but some studies report a rate as high as 32%.⁷ In addition, 38% of patients with celiac disease who consume a gluten-free diet fulfill the symptom-based Rome criteria for IBS.⁷

The contribution of gluten to IBS does not end with the coexistence of IBS and celiac disease, but also includes the newly debated diagnosis of nonceliac gluten sensitivity, characterized by gastrointestinal symptoms (abdominal pain, diarrhea, constipation, nausea, and vomiting) and other symptoms (headache, musculoskeletal pain, “brain fog,” fatigue, and depression) that are similar to those of IBS. Symptoms are triggered by the ingestion of wheat products, are improved after wheat products are removed from the diet, and relapse after a wheat challenge.⁷

Nonceliac gluten sensitivity is often perceivable by patients, resulting in self-diagnosis and self-treatment.⁴ However, it is not clear whether it is gluten or the fructans and galactans in wheat that are responsible for triggering their symptoms.⁷

DIETARY GUIDANCE IS NEEDED

A low-FODMAP diet with small amounts of insoluble dietary fiber improves symptoms and quality of life in patients with IBS, but dietary guidance is critical and should be personalized because patients differ in how they tolerate foods rich in FODMAPs, probably owing to differing intestinal microbiota among individuals.^3,8 Intake of probiotics increases tolerance of FODMAP-rich foods and should also be recommended.^3,8,9 Because of the rigorous restrictions of the low-FODMAP diet, patients who receive personalized guidance are more inclined to adhere to the diet and to avoid vitamin and mineral deficiencies.⁹

To the Editor: In the article by Drs. Singh et al in your June issue, I was surprised that the role of hepatitis delta wasn’t mentioned as a potential cause of acute liver failure. My understanding is that this peculiar virus can only infect those with hepatitis B surface antigenemia, but when it does, it results in far more serious liver injury, including acute liver failure in some.

To the Editor: In the article by Drs. Singh et al in your June issue, I was surprised that the role of hepatitis delta wasn’t mentioned as a potential cause of acute liver failure. My understanding is that this peculiar virus can only infect those with hepatitis B surface antigenemia, but when it does, it results in far more serious liver injury, including acute liver failure in some.

To the Editor: In the article by Drs. Singh et al in your June issue, I was surprised that the role of hepatitis delta wasn’t mentioned as a potential cause of acute liver failure. My understanding is that this peculiar virus can only infect those with hepatitis B surface antigenemia, but when it does, it results in far more serious liver injury, including acute liver failure in some.

In Reply: We thank Dr. Homler for bringing hepatitis D as a potential cause of acute liver failure to our attention.

Hepatitis D virus, first described in the 1970s, requires the hepatitis B surface antigen (HBsAg) capsid to enter the hepatocyte and, thus, can only cause liver injury when the patient is also infected simultaneously with hepatitis B virus.¹ Hepatitis D virus can cause either coinfection (presence of immunoglobulin M anti-HB core antibody with or without HBsAg) or superinfection (presence of HBsAg without immunoglobulin M anti-HB core antibody) with hepatitis B virus. In India, coinfection has been reported to be the cause of acute liver failure in about 4% of all patients, and superinfection in 4.5%.²

While simultaneous treatment for hepatitis D and B viruses with pegylated interferon and any of the agents used for treatment of hepatitis B has been successful in treating chronic hepatitis, it has not been proven useful in patients with acute liver failure, and liver transplant remains the only treatment option.³

In Reply: We thank Dr. Homler for bringing hepatitis D as a potential cause of acute liver failure to our attention.

Hepatitis D virus, first described in the 1970s, requires the hepatitis B surface antigen (HBsAg) capsid to enter the hepatocyte and, thus, can only cause liver injury when the patient is also infected simultaneously with hepatitis B virus.¹ Hepatitis D virus can cause either coinfection (presence of immunoglobulin M anti-HB core antibody with or without HBsAg) or superinfection (presence of HBsAg without immunoglobulin M anti-HB core antibody) with hepatitis B virus. In India, coinfection has been reported to be the cause of acute liver failure in about 4% of all patients, and superinfection in 4.5%.²

While simultaneous treatment for hepatitis D and B viruses with pegylated interferon and any of the agents used for treatment of hepatitis B has been successful in treating chronic hepatitis, it has not been proven useful in patients with acute liver failure, and liver transplant remains the only treatment option.³

In Reply: We thank Dr. Homler for bringing hepatitis D as a potential cause of acute liver failure to our attention.

Hepatitis D virus, first described in the 1970s, requires the hepatitis B surface antigen (HBsAg) capsid to enter the hepatocyte and, thus, can only cause liver injury when the patient is also infected simultaneously with hepatitis B virus.¹ Hepatitis D virus can cause either coinfection (presence of immunoglobulin M anti-HB core antibody with or without HBsAg) or superinfection (presence of HBsAg without immunoglobulin M anti-HB core antibody) with hepatitis B virus. In India, coinfection has been reported to be the cause of acute liver failure in about 4% of all patients, and superinfection in 4.5%.²

While simultaneous treatment for hepatitis D and B viruses with pegylated interferon and any of the agents used for treatment of hepatitis B has been successful in treating chronic hepatitis, it has not been proven useful in patients with acute liver failure, and liver transplant remains the only treatment option.³

To the Editor: I read the excellent overview article on measles by Drs. Kumar and Sabella.¹ However, there are additional important clinical points regarding measles diagnosis that deserve further comment. Prior to definitive diagnosis, measles is a clinical diagnosis. Properly, much attention is given to the rash, but there are important clinical clues besides the rash that are helpful diagnostically.

Some clinical findings are more characteristic of a disease than others, eg, eye findings in measles, and clinicians should specifically look for them. Other findings not characteristic but consistent with the diagnosis are less helpful, eg, measles with diarrhea.² Measles is a systemic infection with several extradermatologic manifestations. Characteristically, measles involves the respiratory tract, manifested by runny nose, dry cough, or shortness of breath, ie, measles pneumonia.²

Gastrointestinal involvement may be manifested as nausea, vomiting, diarrhea, or abdominal pain. Abdominal pain, when located in the right lower quadrant, may mimic acute appendicitis, ie, pseudoappendicitis. In patients undergoing appendectomy, pathologically the appendix is normal but contains multinucleated giant cells (Warthin-Finkeldey cells). Measles pseudoappendicitis can be perplexing because it presents before the rash. Even without appendiceal involvement (pseudoappendicitis), Warthin-Finkeldey cells are also present in the nasal mucosa. If nasal swab cytology shows Warthin-Finkeldey cells, an early diagnosis of measles may be made days before IgM measles antibodies are reported.³

Other often-overlooked important clues are eye findings, eg, watery eyes, lower lid edema, conjunctival suffusion, and keratitis. No other disease in the differential diagnosis of measles presents with watery eyes with bilateral lower lid edema and conjunctival suffusion. Headache, mental confusion or oral ulcers may suggest alternate diagnoses. Typically, nonspecific laboratory abnormalities include leukopenia and thrombocytopenia, and importantly, the erythrocyte sedimentation rate is not elevated (Table 1).^4,5

In measles, much is made of Koplik spots, which are found early on dark red buccal mucosa (vs Fordyce spots).¹ However, if these are missed or not present, clinicians can use other characteristic findings to make a presumptive diagnosis of measles.

To the Editor: I read the excellent overview article on measles by Drs. Kumar and Sabella.¹ However, there are additional important clinical points regarding measles diagnosis that deserve further comment. Prior to definitive diagnosis, measles is a clinical diagnosis. Properly, much attention is given to the rash, but there are important clinical clues besides the rash that are helpful diagnostically.

Some clinical findings are more characteristic of a disease than others, eg, eye findings in measles, and clinicians should specifically look for them. Other findings not characteristic but consistent with the diagnosis are less helpful, eg, measles with diarrhea.² Measles is a systemic infection with several extradermatologic manifestations. Characteristically, measles involves the respiratory tract, manifested by runny nose, dry cough, or shortness of breath, ie, measles pneumonia.²

Gastrointestinal involvement may be manifested as nausea, vomiting, diarrhea, or abdominal pain. Abdominal pain, when located in the right lower quadrant, may mimic acute appendicitis, ie, pseudoappendicitis. In patients undergoing appendectomy, pathologically the appendix is normal but contains multinucleated giant cells (Warthin-Finkeldey cells). Measles pseudoappendicitis can be perplexing because it presents before the rash. Even without appendiceal involvement (pseudoappendicitis), Warthin-Finkeldey cells are also present in the nasal mucosa. If nasal swab cytology shows Warthin-Finkeldey cells, an early diagnosis of measles may be made days before IgM measles antibodies are reported.³

Other often-overlooked important clues are eye findings, eg, watery eyes, lower lid edema, conjunctival suffusion, and keratitis. No other disease in the differential diagnosis of measles presents with watery eyes with bilateral lower lid edema and conjunctival suffusion. Headache, mental confusion or oral ulcers may suggest alternate diagnoses. Typically, nonspecific laboratory abnormalities include leukopenia and thrombocytopenia, and importantly, the erythrocyte sedimentation rate is not elevated (Table 1).^4,5

In measles, much is made of Koplik spots, which are found early on dark red buccal mucosa (vs Fordyce spots).¹ However, if these are missed or not present, clinicians can use other characteristic findings to make a presumptive diagnosis of measles.

To the Editor: I read the excellent overview article on measles by Drs. Kumar and Sabella.¹ However, there are additional important clinical points regarding measles diagnosis that deserve further comment. Prior to definitive diagnosis, measles is a clinical diagnosis. Properly, much attention is given to the rash, but there are important clinical clues besides the rash that are helpful diagnostically.

Some clinical findings are more characteristic of a disease than others, eg, eye findings in measles, and clinicians should specifically look for them. Other findings not characteristic but consistent with the diagnosis are less helpful, eg, measles with diarrhea.² Measles is a systemic infection with several extradermatologic manifestations. Characteristically, measles involves the respiratory tract, manifested by runny nose, dry cough, or shortness of breath, ie, measles pneumonia.²

Gastrointestinal involvement may be manifested as nausea, vomiting, diarrhea, or abdominal pain. Abdominal pain, when located in the right lower quadrant, may mimic acute appendicitis, ie, pseudoappendicitis. In patients undergoing appendectomy, pathologically the appendix is normal but contains multinucleated giant cells (Warthin-Finkeldey cells). Measles pseudoappendicitis can be perplexing because it presents before the rash. Even without appendiceal involvement (pseudoappendicitis), Warthin-Finkeldey cells are also present in the nasal mucosa. If nasal swab cytology shows Warthin-Finkeldey cells, an early diagnosis of measles may be made days before IgM measles antibodies are reported.³

Other often-overlooked important clues are eye findings, eg, watery eyes, lower lid edema, conjunctival suffusion, and keratitis. No other disease in the differential diagnosis of measles presents with watery eyes with bilateral lower lid edema and conjunctival suffusion. Headache, mental confusion or oral ulcers may suggest alternate diagnoses. Typically, nonspecific laboratory abnormalities include leukopenia and thrombocytopenia, and importantly, the erythrocyte sedimentation rate is not elevated (Table 1).^4,5

In measles, much is made of Koplik spots, which are found early on dark red buccal mucosa (vs Fordyce spots).¹ However, if these are missed or not present, clinicians can use other characteristic findings to make a presumptive diagnosis of measles.

In Reply: We thank Dr. Cunha for his comments and appreciate the opportunity to emphasize important points that he highlights.

We agree that measles is a systemic illness with important extradermatologic manifestations that are critical to the diagnosis, and that the nondermatologic manifestations often precede the rash and serve to distinguish measles from other systemic illnesses. As discussed in our review, the respiratory prodrome of cough, coryza, and conjunctivitis is very distinctive and serves as an important clue to the diagnosis. Likewise, we acknowledge the importance of gastrointestinal findings in measles and note appendicitis as an important complication that is well described. Although Koplik spots are pathognomonic, we do stress that these often are not present at the time of presentation.

Finally, we agree that measles is a clinical diagnosis, and that the clinical manifestations beyond the dermatologic manifestations noted in our review and highlighted by Dr. Cunha are extremely helpful to the clinician in considering the diagnosis.

In Reply: We thank Dr. Cunha for his comments and appreciate the opportunity to emphasize important points that he highlights.

We agree that measles is a systemic illness with important extradermatologic manifestations that are critical to the diagnosis, and that the nondermatologic manifestations often precede the rash and serve to distinguish measles from other systemic illnesses. As discussed in our review, the respiratory prodrome of cough, coryza, and conjunctivitis is very distinctive and serves as an important clue to the diagnosis. Likewise, we acknowledge the importance of gastrointestinal findings in measles and note appendicitis as an important complication that is well described. Although Koplik spots are pathognomonic, we do stress that these often are not present at the time of presentation.

Finally, we agree that measles is a clinical diagnosis, and that the clinical manifestations beyond the dermatologic manifestations noted in our review and highlighted by Dr. Cunha are extremely helpful to the clinician in considering the diagnosis.

In Reply: We thank Dr. Cunha for his comments and appreciate the opportunity to emphasize important points that he highlights.

We agree that measles is a systemic illness with important extradermatologic manifestations that are critical to the diagnosis, and that the nondermatologic manifestations often precede the rash and serve to distinguish measles from other systemic illnesses. As discussed in our review, the respiratory prodrome of cough, coryza, and conjunctivitis is very distinctive and serves as an important clue to the diagnosis. Likewise, we acknowledge the importance of gastrointestinal findings in measles and note appendicitis as an important complication that is well described. Although Koplik spots are pathognomonic, we do stress that these often are not present at the time of presentation.

Finally, we agree that measles is a clinical diagnosis, and that the clinical manifestations beyond the dermatologic manifestations noted in our review and highlighted by Dr. Cunha are extremely helpful to the clinician in considering the diagnosis.

To the Editor: As a primary care physician who has practiced for 31 years, I have a few concerns about the article “Prescribing opioids in primary care: Safely starting, monitoring, and stopping” by Drs. Daniel Tobin, Rebecca Andrews, and William Becker in your March 2016 issue.

Prescribing narcotics and other controlled medications has become a hot topic with legal implications. Many physicians have lost their license, and some have lost their freedom as well.

The article notes that primary care physicians provide most of the care for chronic pain but implies that we don’t know what we are doing. Although we might not have completed a residency in the management of chronic pain, we were required to attend a graduate medical school and to complete residency programs. We are also required to read the medical literature and keep up with our CME requirements. We too strive to keep up with and practice the latest cutting-edge medicine. And we have experience. After seeing thousands of patients and writing millions of prescriptions, I think I do know something about whether or not a medicine is safe, effective, and cost-effective. I have encountered quite a few patients with pain, and not one of them has overdosed by taking the medications as prescribed.

Most of what is being said and published about pain medication focuses on the epidemic of young people who are getting pain medications (prescription narcotics) and street narcotics (heroin) illegally. Directly, it has nothing to do with conscientious physicians prescribing narcotics for pain, but indirectly, it has to do with all adults in society. We are allowing our young people to be destroyed by drugs and by a lack of proper discipline in our homes that spills over into society. Where are our children getting these drugs, and who is bringing them into our neighborhoods? The practice of medicine is not the primary problem. I am for scientific, conscientious regulations concerning controlled substances. Medicine needs to inform all doctors about the changing laws surrounding the prescribing of controlled substances.

Cigarettes and alcohol are sold on every corner, and places selling marijuana are popping up everywhere. The former two drugs are harming and killing more young people than all the illegal drugs combined, and marijuana is fast approaching number three. I feel we need to stop picking on the medical profession and stop trying to blame it for all the woes that our young people are encountering every day. The reality is that legal and illegal drugs are not going to go away. We need to love our children more and better prepare them while in our homes to deal with the evils in our society.

To the Editor: As a primary care physician who has practiced for 31 years, I have a few concerns about the article “Prescribing opioids in primary care: Safely starting, monitoring, and stopping” by Drs. Daniel Tobin, Rebecca Andrews, and William Becker in your March 2016 issue.

Prescribing narcotics and other controlled medications has become a hot topic with legal implications. Many physicians have lost their license, and some have lost their freedom as well.

The article notes that primary care physicians provide most of the care for chronic pain but implies that we don’t know what we are doing. Although we might not have completed a residency in the management of chronic pain, we were required to attend a graduate medical school and to complete residency programs. We are also required to read the medical literature and keep up with our CME requirements. We too strive to keep up with and practice the latest cutting-edge medicine. And we have experience. After seeing thousands of patients and writing millions of prescriptions, I think I do know something about whether or not a medicine is safe, effective, and cost-effective. I have encountered quite a few patients with pain, and not one of them has overdosed by taking the medications as prescribed.

Most of what is being said and published about pain medication focuses on the epidemic of young people who are getting pain medications (prescription narcotics) and street narcotics (heroin) illegally. Directly, it has nothing to do with conscientious physicians prescribing narcotics for pain, but indirectly, it has to do with all adults in society. We are allowing our young people to be destroyed by drugs and by a lack of proper discipline in our homes that spills over into society. Where are our children getting these drugs, and who is bringing them into our neighborhoods? The practice of medicine is not the primary problem. I am for scientific, conscientious regulations concerning controlled substances. Medicine needs to inform all doctors about the changing laws surrounding the prescribing of controlled substances.

Cigarettes and alcohol are sold on every corner, and places selling marijuana are popping up everywhere. The former two drugs are harming and killing more young people than all the illegal drugs combined, and marijuana is fast approaching number three. I feel we need to stop picking on the medical profession and stop trying to blame it for all the woes that our young people are encountering every day. The reality is that legal and illegal drugs are not going to go away. We need to love our children more and better prepare them while in our homes to deal with the evils in our society.

To the Editor: As a primary care physician who has practiced for 31 years, I have a few concerns about the article “Prescribing opioids in primary care: Safely starting, monitoring, and stopping” by Drs. Daniel Tobin, Rebecca Andrews, and William Becker in your March 2016 issue.

Prescribing narcotics and other controlled medications has become a hot topic with legal implications. Many physicians have lost their license, and some have lost their freedom as well.

The article notes that primary care physicians provide most of the care for chronic pain but implies that we don’t know what we are doing. Although we might not have completed a residency in the management of chronic pain, we were required to attend a graduate medical school and to complete residency programs. We are also required to read the medical literature and keep up with our CME requirements. We too strive to keep up with and practice the latest cutting-edge medicine. And we have experience. After seeing thousands of patients and writing millions of prescriptions, I think I do know something about whether or not a medicine is safe, effective, and cost-effective. I have encountered quite a few patients with pain, and not one of them has overdosed by taking the medications as prescribed.

Most of what is being said and published about pain medication focuses on the epidemic of young people who are getting pain medications (prescription narcotics) and street narcotics (heroin) illegally. Directly, it has nothing to do with conscientious physicians prescribing narcotics for pain, but indirectly, it has to do with all adults in society. We are allowing our young people to be destroyed by drugs and by a lack of proper discipline in our homes that spills over into society. Where are our children getting these drugs, and who is bringing them into our neighborhoods? The practice of medicine is not the primary problem. I am for scientific, conscientious regulations concerning controlled substances. Medicine needs to inform all doctors about the changing laws surrounding the prescribing of controlled substances.

Cigarettes and alcohol are sold on every corner, and places selling marijuana are popping up everywhere. The former two drugs are harming and killing more young people than all the illegal drugs combined, and marijuana is fast approaching number three. I feel we need to stop picking on the medical profession and stop trying to blame it for all the woes that our young people are encountering every day. The reality is that legal and illegal drugs are not going to go away. We need to love our children more and better prepare them while in our homes to deal with the evils in our society.

In Reply: We thank Dr. Pettiway for his remarks. The intent of our article was to identify common challenges when prescribing opioids for chronic pain and offer tips to the provider struggling with how to do so safely. We hope these comments will offer additional clarity.

First, as general internists who are essentially “self-trained” in the management of chronic pain, we fully acknowledge the importance of practical experience in learning how to prescribe opioids safely and effectively. Dr. Pettiway is correct that a dedicated physician who keeps up with the medical literature, attends relevant continuing medical education courses, and strives to provide deliberate, rational, and evidence-based care to his or her patients can do so effectively. However, the medical literature suggests that medical school training in the management of chronic pain is sparse; one review found that in 2011 only 5 out of 133 US medical schools required coursework on pain management, and only 13 offered it as an elective.¹ Many primary care providers do feel unprepared to handle this challenge.

Additionally, Dr. Pettiway raises a good question about where misused prescription opioids originate and whether prescribers are responsible. The data show that the majority of misused prescription opioids are obtained from a family member or friend and not directly from a physician.^2,3 However, this supply does generally originate from a prescription. Providers need to educate their patients about the risk for diversion, the need to keep pills safely hidden and locked away, and the importance of safely discarding unused supplies. Responsible prescribers need to anticipate these concerns and educate patients about them.

In summary, we firmly believe that primary care providers are capable of safe, effective, and responsible opioid prescribing and hope that our paper provides additional guidance on how to do so.

In Reply: We thank Dr. Pettiway for his remarks. The intent of our article was to identify common challenges when prescribing opioids for chronic pain and offer tips to the provider struggling with how to do so safely. We hope these comments will offer additional clarity.

First, as general internists who are essentially “self-trained” in the management of chronic pain, we fully acknowledge the importance of practical experience in learning how to prescribe opioids safely and effectively. Dr. Pettiway is correct that a dedicated physician who keeps up with the medical literature, attends relevant continuing medical education courses, and strives to provide deliberate, rational, and evidence-based care to his or her patients can do so effectively. However, the medical literature suggests that medical school training in the management of chronic pain is sparse; one review found that in 2011 only 5 out of 133 US medical schools required coursework on pain management, and only 13 offered it as an elective.¹ Many primary care providers do feel unprepared to handle this challenge.

Additionally, Dr. Pettiway raises a good question about where misused prescription opioids originate and whether prescribers are responsible. The data show that the majority of misused prescription opioids are obtained from a family member or friend and not directly from a physician.^2,3 However, this supply does generally originate from a prescription. Providers need to educate their patients about the risk for diversion, the need to keep pills safely hidden and locked away, and the importance of safely discarding unused supplies. Responsible prescribers need to anticipate these concerns and educate patients about them.

In summary, we firmly believe that primary care providers are capable of safe, effective, and responsible opioid prescribing and hope that our paper provides additional guidance on how to do so.

In Reply: We thank Dr. Pettiway for his remarks. The intent of our article was to identify common challenges when prescribing opioids for chronic pain and offer tips to the provider struggling with how to do so safely. We hope these comments will offer additional clarity.

First, as general internists who are essentially “self-trained” in the management of chronic pain, we fully acknowledge the importance of practical experience in learning how to prescribe opioids safely and effectively. Dr. Pettiway is correct that a dedicated physician who keeps up with the medical literature, attends relevant continuing medical education courses, and strives to provide deliberate, rational, and evidence-based care to his or her patients can do so effectively. However, the medical literature suggests that medical school training in the management of chronic pain is sparse; one review found that in 2011 only 5 out of 133 US medical schools required coursework on pain management, and only 13 offered it as an elective.¹ Many primary care providers do feel unprepared to handle this challenge.

Additionally, Dr. Pettiway raises a good question about where misused prescription opioids originate and whether prescribers are responsible. The data show that the majority of misused prescription opioids are obtained from a family member or friend and not directly from a physician.^2,3 However, this supply does generally originate from a prescription. Providers need to educate their patients about the risk for diversion, the need to keep pills safely hidden and locked away, and the importance of safely discarding unused supplies. Responsible prescribers need to anticipate these concerns and educate patients about them.

In summary, we firmly believe that primary care providers are capable of safe, effective, and responsible opioid prescribing and hope that our paper provides additional guidance on how to do so.