Conference Coverage

For cancer prevention, not all plant-based diets are equal



Following a diet rich in healthy plant-based products may lower one’s risk of breast cancer, but not if that diet happens to be high in unhealthy foods, researchers have found.

The study of more than 65,000 people showed that plant-based diets that were high in whole grains, fruits, and vegetables appear to be more protective against breast cancer than diets rich in processed plant-based products, such as juice and chips.

“Results suggest that the best plant-based diet for breast cancer prevention could be a healthy plant-based diet comprising fruit, vegetables, whole grains, nuts, and legumes,” said Sanam Shah, MBBS, FCPS, MPH, a doctoral candidate in epidemiology at Paris-Saclay University, who is the lead author of the new study. “In contrast, an unhealthy plant-based diet comprising higher intakes of primarily processed products of plant origin, such as refined grains, fruit juices, sweets, desserts, and potatoes, would be worse for breast cancer prevention.”

Dr. Shah’s group is presenting their research online at the annual meeting of the American Society for Nutrition.

Although the role of plant-based diets in cancer prevention has received extensive attention, Dr. Shah said few studies have assessed the influence of the quality of those diets on the risk of breast cancer.

Dr. Shah and colleagues conducted a prospective cohort study to investigate the link between healthy and unhealthy plant-based diets and breast cancer risk. Unlike other studies, the researchers also evaluated the effect of a gradual decrease in animal products in diets on health.

Dr. Shah’s group followed 65,574 postmenopausal women in France (mean age, 52.8 years) from 1993 to 2014. The researchers used self-reported food questionnaires to classify women into groups on the basis of adherence to a mostly plant or animal diet. Plant-based diets did not exclude meat but had more plant than animal products, Dr. Shah said. The researchers also grouped women on the basis of how healthy the plant-based diets were.

Over the 21-year study period, 3,968 women were diagnosed with breast cancer. Those who adhered to a more healthful plant-based diet had a 14% lower risk than average of developing breast cancer, while those who adhered to a less healthful plant-based diet had a 20% greater risk of developing the disease.

Nutritional quality varies greatly across plant-based foods. Quality plant-based diets should focus on variety to avoid nutritional deficiencies in iron, zinc, calcium, and vitamin B12, Dr. Shah said.

“The study by Shah and coworkers underscores the importance of considering more global aspects of the diet rather than single components when examining relationships between diet and health,” said Megan McCrory, PhD, research associate professor of nutrition at Boston University. “As the study illustrates, plant-based diets as a whole are not always healthy and may also contain less desirable nutrients and foods.”

Abstracts in the conference have been selected by a board of experts for presentation but have not yet been peer reviewed. All findings are to be regarded as preliminary until they are published in peer-reviewed articles. Dr. Shah and Dr. McCrory disclosed no relevant financial relationships.

A version of this article first appeared on

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