Adherence to Plant-Based Diets Can Reduce Risk of Diabetes, Harvard Study Finds

Frank Hu, MD

Adherence to a diet composed of healthy, plant-based foods is associated with a lower risk of developing type 2 diabetes, according to a recent study from the Harvard T.H. Chan School of Public Health.

An analysis of data from 3 prospective cohorts totaling more than 10,000 participants, results of the study detail an inverse association between adherence to plant-based diets and risk of type 2 diabetes when assessing adherence using metabolic profile scores for 3 indices derived from food frequency questionnaires.

“While it is difficult to tease out the contributions of individual foods because they were analyzed together as a pattern, individual metabolites from consumption of polyphenol-rich plant foods like fruits, vegetables, coffee, and legumes are all closely linked to healthy plant-based diet and lower risk of diabetes,” said lead investigator Frank Hu, MD, PhD, a professor in the Department of Nutrition at the Harvard T.H. Chan School of Public Health, in a statement.

With the obesity epidemic continuing to balloon and with it the subsequent impact on health systems, the impact of dietary choices and nutrition has become a renewed focus in research. As such, Hu and a team of colleagues from Harvard T.H. Chan School of Public Health sought to assess identify different metabolite profiles associated with plant-based diets and how these metabolites might influence risk of developing type 2 diabetes.

To do so, investigators designed their study as an analysis of data from blood plasma samples and dietary intake information among participants from the Nurses’ Health Study, Nurses’ Health Study II, and Health Professionals Follow-up Study. The mean age of these patients was 54 years and the mean BMI was 25.6 kg/m2. All patients included in these studies provided data related to dietary adherence on food frequency questionnaires. The plant-based diet indices of interest in the current study were the overall Plant-based Diet Index (PDI), a healthy Plant-based Diet Index (hPDI), and an Unhealthy Plant-Based Diet Index (uPDI).

In their analyses, investigators used Cox proportional hazards regression to assess prospective associations between metabolite profiles and incident type 2 diabetes. For the purpose of analysis, investigators identified multi-metabolite profiles comprising 55 metabolites for PDI, 93 metabolites for hPDI and 75 metabolites for uPDI.

Upon analysis, investigators found metabolite profiles were correlated with the corresponding diet index (Pearson r = 0.33–0.35 for PDI, 0.41–0.45 for hPDI, and 0.37–0.38 for uPDI; P for all <.001). Investigators pointed out metabolite profile scores of PDI (HR per 1 SD higher, 0.81 [95% CI 0.75-0.88]) and hPDI (HR per 1 SD higher, 0.77 [95% CI 0.71-0.84]) had an inverse association with incident type 2 diabetes, while the metabolite profile score for uPDI was not associated with increased risk of incident type 2 diabetes.

Further analysis demonstrated adjustment for metabolites selected in metabolite profiles attenuated association of diet indices with PDI and hPDI with lower type 2 diabetes risk. Additionally, investigators noted the explainable proportion of PDI/hPDI-related diabetes risk ranged from 8.5-37.2% (P for all <.05).

“Our findings support the beneficial role of healthy plant-based diets in diabetes prevention and provide new insights for future investigation…our findings regarding the intermediate metabolites are at the moment intriguing but further studies are needed to confirm their causal role in the associations of plant-based diets and the risk of developing type 2 diabetes,” wrote investigators.

This study, “Plasma metabolite profiles related to plant-based diets and the risk of type 2 diabetes,” was published in Diabetologia.