New research shows that adding variety, especially more plant proteins, to your plate could help prevent type 2 diabetes, with notable benefits for women and people without central obesity.
Study: Protein diversity, type 2 diabetes, and effect modifiers: a multi-country prospective study. Image Credit: margouillat photo / Shutterstock
In a recent study published in the International Journal of Epidemiology, researchers investigated the associations between dietary diversity and the incidence of type 2 diabetes (T2D).
Diabetes affected over 10% of the global population in 2021, with T2D accounting for about 90% of diabetes diagnoses and a majority of related burdens. Therefore, the prevention of T2D remains a policy and healthcare priority. Diet is recognized as a modifiable factor in T2D prevention. Dietary diversity is a vital aspect of healthy eating, and unlike quantity, quality, or frequency of food intake, it reflects the variety of foods consumed.
A healthy diet may lack diversity, and a diverse diet may not necessarily contain lower salt, trans fats, or energy. The diversity of protein-rich foods is important for health and T2D management. Further, evidence suggests that total protein intake influences T2D risk. For instance, higher amounts of animal protein increase the risk of T2D, while there is no association with the quantity of plant protein. Additionally, the risk of T2D varies by animal protein subtype.
A higher quantity of processed and red meat increases T2D incidence, while dairy products appear protective. Various protein-rich foods contain numerous bioactive compounds, and the biological effects and relative contribution of protein intake may vary based on whether the diet is diverse in animal or plant protein. However, no study has investigated the diversity in protein-rich foods by dietary source.
About the study
The present study investigated the associations between dietary diversity and the incidence of T2D. Data were obtained from the EPIC-InterAct study. Five diet diversity scores (DDSs) were derived from self-reported dietary data. These included diversity of food groups (DDS-total5) and diversity within subtypes of vegetables (DDS-veg), meat and alternative (DDS-meat), animal protein (DDS-ProtA), and plant protein (DDS-ProtP).
Food groups included grain, dairy products, fruits, vegetables, meat, and alternative sources. Vegetable subtypes were root, leafy, fruiting, and other vegetables. Plant protein subtypes included legumes, nuts and seeds, rice and pasta, bread, and other cereals. Meat and alternative subtypes were red and processed meat, poultry, organ meat, fish and seafood, eggs, legumes, seeds, and nuts.
Animal protein subtypes included processed meat, red meat, cheese, milk and dairy products, organ meat, fish and seafood, poultry, and eggs. Prentice-weighted Cox regression models were used to evaluate prospective associations between each DDS and T2D incidence, stratified by sex and obesity status. Cox regression analyses were performed to assess effect modification by sex and obesity.
Findings
The study population comprised 23,649 individuals from eight European countries, including 10,363 incident cases of T2D. On average, subjects were followed up for 9.9 years or 234,324 person-years. The intake of four or five plant protein sources was associated with a reduced T2D incidence across countries compared to no intake.
Besides, consuming every new plant protein subtype was associated with a 4% lower T2D incidence. Plant protein diversity was inversely associated with the incidence of T2D in females. The incidence of T2D was 25% lower in females consuming three plant protein subtypes. Moreover, while plant protein diversity showed an inverse association with T2D incidence in individuals both with and without obesity, the result was only statistically significant for those without central obesity.
However, individuals without central obesity who consumed four to five subtypes of plant protein had an 18% lower T2D incidence, a finding that was borderline significant (HR 0.82, 95% CI 0.68-1.00). For DDS-total5 and DDS-veg, the highest scores were associated with reduced incidence of T2D compared to the lowest scores. Each additional food group in the diet was associated with a 9% lower T2D incidence. The intake of the five food groups was associated with a lower incidence of T2D in females (HR 0.86, 95% CI 0.77-0.96), and while a similar pattern was observed in males, the association was not statistically significant for them (HR 0.84, 95% CI 0.68-1.04).
Consuming at least three different types of vegetables decreased the incidence of T2D in males by 15% (HR 0.85, 95% CI 0.73-0.99). Likewise, the intake of four and five major food groups reduced the incidence of T2D by 17% and 21% in individuals without central obesity. No clear associations were identified for DDS-ProtA and DDS-meat. Nevertheless, higher DDS-meat was associated with incident T2D in people without central obesity. Interestingly, some of these findings were contrary to the researchers' initial hypothesis that greater diversity would be more protective for males and individuals with obesity. It is also important to note that while trends sometimes differed between subgroups, the paper reported that the formal statistical tests for these interactions were often not significant, urging a cautious interpretation of these differences.
Conclusions
In summary, consuming four or five different plant-protein sources was consistently associated with a reduced risk of T2D incidence compared to no intake of these sources. Consuming four subtypes of vegetables and five major food groups was also associated with a lower T2D risk.
However, the researchers noted that some of these associations were weakened when they performed additional analyses. For instance, the link between vegetable diversity and lower T2D risk in males was no longer statistically significant after accounting for other dietary diversity scores, suggesting the findings should be interpreted with caution.
The study's authors also pointed out several limitations. The findings rely on self-reported dietary data collected at a single point in time, which may not capture changes in diet over the years. Furthermore, because the study population was European, the results may not be generalizable to other populations.
Overall, these findings support the dietary guidelines for consuming foods from five food groups and incorporating a variety of vegetables and plant-based proteins into the diet.