Consumption of healthy plant-based foods, such as fruits, vegetables, nuts, coffee, and legumes, is linked to a lower risk of developing type 2 diabetes (T2D) in generally healthy people, according to new research published in Diabetologia (the journal of the European Association for the Study of Diabetes (EASD)).
Professor Frank Hu and colleagues at Harvard T.H. Chan School of Public Health, Boston, MA, USA, conducted the study, which aimed to discover metabolite profiles associated with various plant-based diets and evaluate any correlations between those profiles and the risk of developing T2D.
The large amount of substances found in various diets, as well as the complex diversity of molecules created as those compounds are broken down and converted for use by the body, are all examples of metabolites.
Because foods have different chemical compositions, an individual’s metabolite profile should mirror their diet. The advent of high-throughput metabolomics profiling has ushered in a new era of nutritional study. The comprehensive examination and identification of all the various metabolites present inside a biological sample is known as metabolomics.
Type 2 diabetes accounts for over 90% of all diabetes occurrences, and it is a major health problem around the world. In less than two decades, the global frequency of the disease in adults has more than quadrupled, with instances rising from roughly 150 million in 2000 to over 450 million in 2019, with a projected rise to around 700 million in 2045.
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.Professor Frank Hu
The disease’s various consequences, both macrovascular, such as cardiovascular disease, and microvascular, exacerbate T2D’s worldwide health impact which affect the kidneys, eyes, and neurological system.
Unhealthy diets, being overweight or obese, genetic susceptibility, and other lifestyle factors such as a lack of exercise are the primary causes of diabetes. Plant-based diets, particularly those that are high in high-quality foods such whole grains, fruits, and vegetables, have been linked to a lower incidence of T2D, although the underlying mechanisms are yet unknown.
The researchers analyzed blood plasma samples and food consumption of 10,684 people from three prospective cohorts (Nurses’ Health Study. The majority of the participants were white, middle-aged (mean age 54 years), and had a BMI of 25.6kg/m2.
Participants filled out food frequency questionnaires (FFQs) that were assessed based on their adherence to one of three plant-based diets: an overall Plant-based Diet Index (PDI), a healthy Plant-based Diet Index (hPDI), or an Unhealthy Plant-Based Diet Index (uPDI).
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); and animal foods (animal fats, dairy, eggs, fish/seafood, meat, and miscellaneous animal-based foods) were used to create diet indices.
The researchers classified plant foods as healthy or unhealthy based on their links to T2D, cardiovascular disease, some malignancies, and other disorders like obesity and high blood pressure.
The researchers used blood samples taken in the early stages of the three studies listed above to establish metabolite profile scores for the participants, and any incidences of incident T2D were recorded during the study’s follow-up period. The team was able to uncover any associations between metabolite profile, diet index, and T2D risk by analyzing these data along with the diet index scores.
Participants who were diagnosed with T2D during follow-up had a lower intake of healthful plant-based foods, as well as lower PDI and hPDI scores, compared to those who did not develop the condition.
They were also more likely to have high blood pressure and cholesterol levels, take blood pressure and cholesterol medications, have a family history of diabetes, and be less physically active.
Plant-based diets were linked to distinct multi-metabolite profiles, which differed considerably between healthy and harmful plant-based diets, according to the metabolomics data.
Furthermore, 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 the unhealthy plant-based diet had no such association.
As a consequence, higher metabolite profile scores for PDI and hPDI suggested both better diet adherence and a lower risk of T2D.
After controlling for levels of trigonelline, hippurate, isoleucine, a small set of triacyglycerols (TAGs), and numerous other intermediate metabolites, the link between plant-based diets and T2D essentially vanished, implying that they may play a crucial role in linking those diets to incident diabetes.
Trigonelline, for example, is found in coffee and has been shown in animal studies to reduce insulin resistance, while higher levels of hippurate are linked to better glycaemic management, increased insulin secretion, and a lower incidence of T2D.
The researchers believe that these metabolites should be explored further because they could provide mechanistic reasons for how plant-based diets can reduce T2D risk.
Professor Hu explains: “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 healthy plant-based diet and lower risk of diabetes.”
The authors conclude: “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.”
The scientists believe that long-term repeated metabolomics data is needed to understand how dietary changes connect to changes in the metabolome, hence increasing T2D risk, because they only collected blood samples at one point in time.