Healthy plant-based diet reduces breast cancer risk

Long-term adherence to a healthy plant-based diet was associated with a 14% lower risk for breast cancer among postmenopausal women, according to findings presented at the virtual meeting of the American Society of Nutrition.

In contrast, researchers reported that adherence to an unhealthy plant-based diet was associated with a 20% greater breast cancer risk.

“These findings have implications for all subtypes of breast cancer,” Sanam Shah, MBBS, FCPS, MPH, a doctoral candidate in the Center for Research in Epidemiology and Population Health at Paris-Saclay University, Inserm, Gustave Roussy in France, said during the presentation. “The results support the importance of the quality of plant-based foods and consuming plant-predominant diets.”

Previous research has demonstrated the beneficial effects of vegan and vegetarian diets on health outcomes, according to Shah and colleagues. However, few studies have examined how the healthfulness of plant-based diets impact health, including breast cancer risk.

To learn more, the researchers assessed the association between long-term adherence to a plant-based diet and breast cancer risk among 65,574 postmenopausal women in France. They compared outcomes among women who consumed healthy plant-based foods — such as whole grains, fruit, vegetables, nuts, legumes, vegetable oils and tea or coffee — and unhealthy plant-based foods — such as fruit juices, refined grains, potatoes, sugar-sweetened beverages and desserts.

While plant-based diets primarily consist of foods with plant origin, Shah noted they can also include small quantities of food from animal sources.

“What is different about our study is that we could disentangle the effects of the quality of plant foods, which has not been the focus of previous studies on other dietary patterns,” Shah said in a press release. “By scoring healthy, unhealthy and animal-based foods, we comprehensively analyzed food intake by considering the ‘healthiness’ of food groups.”

For the study, participants filled out dietary intake questionnaires in 1993 and 2005. Over an average follow-up period of 21 years, 3,968 participants were diagnosed with breast cancer.

There were significant differences in breast cancer risk, with a lower risk among those who had the greatest adherence to a healthy plant-based diet, even those that included animal-based foods (HR = 0.86; 95% CI, 0.77-0.95), and a higher risk among women who had the greatest adherence to an unhealthy plant-based diet (HR = 1.2; 95% CI, 1.08-1.33), according to the researchers. Shah said there was no heterogeneity by breast cancer receptor status or histology.

Although the underlying mechanisms of these associations remain unclear, Shah said that high fiber may reduce cancer risk through anti-inflammatory and antioxidant effects.

“In addition, studies have shown that fiber reduces circulating estrogen levels and increases in sex hormone-binding globulin,” she said. “Polyphenols could be responsible for the observed beneficial associations, as well as improved gut microbial profile and insulin sensitivity.”

Conversely, unhealthy foods that are high in sodium, unhealthy fat and sugar and low in fiber and micronutrients have been linked to cancer development.

“Moreover, there could be a loss of antioxidants and prooxidants formation when cooking at high temperatures,” Shah said. “More studies are needed to confirm the findings and better understand the underlying mechanisms involved in these associations. For example, exploring the potential mediating and modifying wall of the gut microbiome on the associations between a plant-based diet and breast cancer.”

References:

For breast cancer prevention, diet quality matters. https://www.eurekalert.org/news-releases/954879. Published June 14, 2022. Accessed June 20, 2022.

Shah S, et al. Adherence to healthy and unhealthy plant-based diets and risk of breast cancer overall and by hormone receptor and histologic subtypes among postmenopausal women. Presented at: American Society of Nutrition Scientific Sessions and Annual Meeting; June 14-16, 2022 (virtual meeting).