A new study finds that following healthy plant-based diets can reduce the risk of developing type 2 diabetes in generally healthy individuals.
Plant-based diets emphasise foods derived from plants such as fruit, vegetables and grains. This diet has a range of health benefits, such as supporting the immune system, and lowering inflammation and now, new research has uncovered the potential effects of plant-based diets on diabetes risk.
The study was conducted by Professor Frank Hu and colleagues at the Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA, and aimed to identify the metabolite profiles related to different plant-based diets and investigate possible associations between those profiles and the risk of developing type 2 diabetes.
The new research was published in Diabetologia, the journal of the European Association for the Study of Diabetes (EASD).
Type 2 diabetes: a global health concern
The research team analysed metabolite, which is a substance used or produced by the chemical processes in a living organism. Research advances in technology in metabolomics profiling, and the comprehensive analysis and identification of different metabolites, have allowed for new nutritional research.
Over 90% of diabetes cases are the type 2 form, and the condition continues to threaten the health of the global population. The diabetes burden is primarily caused by unhealthy diets, being overweight, genetic predisposition and lifestyle factors such as lack of exercise. The association between plant-based diets and type 2 diabetes (T2D) is known, but the underlying mechanism is understudied.
Plant-based diets and diabetes
The research team analysed blood plasma samples and dietary intake of 10,684 participants from three prospective cohorts (Nurses’ Health Study, Nurses’ Health Study II and Health Professionals Follow-up Study). The participants were mostly white, middle-aged (mean age 54 years) and with a mean body mass index of 25.6kg/m2.
The participants partook in food frequency questionnaires (FFQs) which were scored against three plant-based diets, including an overall Plant-based Diet Index (PDI), a healthy Plant-based Diet Index (hPDI), and an unhealthy Plant-Based Diet Index (uPDI). The diets indices were based on the intake of 18 food groups:
- Healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, vegetable oils, and tea/coffee);
- Unhealthy plant foods (refined grains, fruit juices, potatoes, sugar-sweetened beverages, and sweets/desserts);
- Animal foods (animal fats, dairy, eggs, fish/seafood, meat, and miscellaneous animal-based foods).
The team distinguished between healthy and unhealthy plant foods according to their association with T2D, cardiovascular disease, certain cancers, and other conditions, including obesity and high blood pressure.
The research team tested blood samples from the 1980s and 1990s in the early phase of the studies the participants were recruited from. This was in order to create metabolite profile scores for the participants and record any incidents of T2D. Analyses of these data, together with the diet index scores, enabled the team to find any correlations between metabolite profile, diet index, and T2D risk.
The findings of the study
The study found that compared with participants who did not develop T2D, those who were diagnosed with the disease during follow-up had a lower intake of healthy plant-based foods, as well as lower scores for PDI and hPDI. In addition, they had a higher average BMI and were more likely to have high blood pressure and cholesterol levels, use blood pressure and cholesterol drugs, have a family history of diabetes, and be less physically active.
Furthermore, the data revealed that plant-based diets were associated with unique multi-metabolite profiles and that these patterns differed significantly between the healthy and unhealthy plant-based diets. In addition, metabolite profile scores for both the overall plant-based diet and the healthy plant-based diet were inversely associated with incident T2D in a generally healthy population, independent of BMI, and other diabetes risk factors, while no association was observed for the unhealthy plant-based diet. As a result, higher metabolite profile scores for PDI and hPDI indicated both closer adherence to those diets and having a lower risk of developing T2D.
However, further analysis revealed that after adjusting for levels of trigonelline, hippurate, isoleucine, a small set of triacylglycerols (TAGs), and several other intermediate metabolites, the association between plant-based diets and T2D largely disappeared, suggesting that they might play a key role in linking those diets to incident diabetes.
Professor Hu explained: “While it is difficult to tease out the contributions of individual foods because they were analysed together as a pattern, individual metabolites from consumption of polyphenol-rich plant foods like fruits, vegetables, coffee, and legumes are all closely linked to a healthy plant-based diet and lower risk of diabetes.”
The authors concluded: “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.”
Since they only collected blood samples at one point in time, the authors also believe that long-term repeated metabolomics data are needed to understand how dietary changes relate to changes in metabolome, thereby influencing T2D risk.