Eating a diet high in plant foods with little or no red meat has been linked to lower risk of type 2 diabetes in the most comprehensive scrutiny of this connection so far.
This protective effect is even stronger for diets high in healthier plant foods such as fruits, vegetables, whole grains, legumes and nuts.
Diabetes has been called “the fastest growing health crisis of our time”. At the same time, plant-based diets are gaining popularity.
Therefore, the researchers thought it was important to quantify their link with diabetes risk, says first author Frank Qian from the Harvard TH Chan School of Public Health, US – especially given the large variation in these diets.
The analysis, published in the Journal of the American Medical Association, included nine studies with more than 300,000 participants – of whom 23,544 had type 2 diabetes – over two to 28 years of follow-up.
In the primary evaluation, Qian and co-authors focussed on an overall higher intake of plant-based foods along with little or no animal-based foods. Therefore, this included vegetarian or vegan dietary patterns.
They found that people with the highest adherence to predominantly plant-based diets had a 23% reduced risk of type 2 diabetes compared to those with the lowest consumption of plant foods.
But these dietary patterns didn’t exclude plant-derived foods that have been linked to higher diabetes risk, such as sugar and refined carbohydrates.
When narrowing the analysis to four studies that defined a plant-based diet as the healthy whole food options, they found a 30% lower risk of type 2 diabetes.
While it must be noted that the studies are observational, most, if not all, adjusted for well-known risk factors, including body mass index (BMI), gender, smoking status and family history of diabetes, among other potentially confounding variables.
Several factors could explain the associations, the authors say.
Plant-based diets typically include healthy plant foods packed with nutrients, polyphenols and fibre, which can improve insulin sensitivity, lower blood pressure, reduce inflammation and help maintain a healthy weight.
All of these can lower the risk of type 2 diabetes. Conversely, eating red and processed meat has been linked to higher risk.
Because the studies controlled for BMI, and excess weight and type 2 diabetes are a deadly duo, the authors suggest the associations they found could underestimate the actual degree of protection conferred by the diets.