Applied Evidence

Vitamin supplementation in healthy patients: What does the evidence support?

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Vitamin B6

Vitamers: Pyridoxine; pyridoxamine; pyridoxal

Physiologic role: Widely involved coenzyme for cognitive development, neurotransmitter biosynthesis, homocysteine and glucose metabolism, immune function, and hemoglobin formation

Dietary sources: Fish, organ meats, potatoes/starchy vegetables, fruit (other than citrus), and fortified cereals

Pyridoxine is required for numerous enzymatic processes in the body, including biosynthesis of neurotransmitters and homeostasis of the amino acid homocysteine.2 While overt deficiency is rare, marginal insufficiency may become clinically apparent and has been associated with malabsorption, malignancies, pregnancy, heart disease, alcoholism, and use of drugs such as isoniazid, hydralazine, and levodopa/carbidopa.2 Vitamin B6 supplementation is known to decrease plasma homocysteine levels, a theorized intermediary for cardiovascular disease; however, studies have failed to consistently demonstrate patient-­oriented benefits.100-102 While observational data has suggested a correlation between vitamin B6 status and cancer risk, RCTs have not supported benefit from supplementation.14-16 Potential effects of vitamin B6 supplementation on cognitive function have also been studied without observed benefit.17,18

The takeaway: Vitamin B6 is recommended as a potential treatment option for nausea in pregnancy.19 Otherwise, vitamin B6 is readily available in food, deficiency is rare, and no patient-oriented evidence supports supplementation in the general population.

Vitamin B7

Vitamers: Biotin

Physiologic role: Cofactor in the metabolism of fatty acids, glucose, and amino acids. Also plays key role in histone modifications, gene regulation, and cell signaling

Dietary sources: Widely available; most prevalent in organ meats, fish, meat, seeds, nuts, and vegetables (eg, sweet potatoes). Whole cooked eggs are a major source, but raw eggs contain avidin, which blocks absorption

Biotin serves a key role in metabolism, gene regulation, and cell signaling.2 Biotin is known to interfere with laboratory assays— including cardiac enzymes, thyroid studies, and hormone studies—at normal supplementation doses, resulting in both false-positive and false-negative results.103

The takeaway: No evidence supports the health benefits of biotin supplementation.

Vitamin B9

Vitamers: Folates; folic acid

Physiologic role: Functions as a coenzyme in the synthesis of DNA/RNA and metabolism of amino acids

Dietary sources: Highest content in spinach, liver, asparagus, and brussels sprouts. Generally found in green leafy vegetables, fruits, nuts, beans, peas, seafood, eggs, dairy, meat, poultry, grains, and fortified cereals.

Continue to: Vitamin B12


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