Dietary Protein Intake And Risk Of Type 2 Diabetes In US Men And Women, American Journal of Epidemiology, online 28 March 2016.
This was a big, long-term study. There were more than 200,000 participants:
We investigated the associations between total, animal, and vegetable protein and incident type 2 diabetes in 72,992 women from the Nurses’ Health Study (1984–2008), 92,088 women from Nurses’ Health Study II (1991–2009) and 40,722 men from the Health Professionals Follow-up Study (1986–2008).
In conclusion, higher intake of animal protein was associated with an increased risk of type 2 diabetes, while higher intake of vegetable protein was associated with a modestly reduced risk.
Eating a meal of, say, beans instead of red meat, chicken, or eggs could reduce your diabetes risk. That 5% in the quote below is a mere 100 calories in a 2000 calorie diet:
Substituting 5% of energy intake from vegetable protein for animal protein was associated with a 23% reduced risk of type 2 diabetes.
People I know who have diabetes or prediabetes live in fear of carbohydrates. What do they do? They eat more animal foods … meat, eggs, cheese, seafood, and dairy. These foods are indeed lower in carbohydrates than plant foods and can cause blood glucose numbers to go down … in the short term. But in the long term, they increase insulin resistance and make it that much harder to control blood glucose. What do they do then? They eat even more animal foods!
To our knowledge, this is the first study that has examined long-term intake of protein in relation to T2D risk using repeated measurements taken over many years of follow-up and that has examined the role of substitution of protein and protein type by carbohydrate type in T2D risk.
Our results support those of previous studies that have found positive associations between total and animal protein and risk of T2D.
It wasn’t just overweight people for whom animal food increased risk. In fact, leaner people seemed to be more sensitive to it:
In our analysis, associations between total and animal protein and T2D were stronger among participants who had a BMI less than 30.
What counted as vegetable protein?
In our cohorts, the main sources of vegetable protein intake included whole grains, nuts, peanut butter, and beans.
What’s the mechanism? I’ve written about these several times over the years:
Potential biological mechanisms supporting divergent associations of animal and vegetable protein with risk of T2D are unknown but may relate to different protein-rich food sources, co-occurrence of other nutrients in protein-rich foods, and variations in the amino acid composition* of these foods.
In our cohorts, intake of red and processed meat has been positively associated with weight gain (32) and with risk of T2D (6), coronary heart disease (33), stroke (34), and mortality (35). Various nutrients in red and processed meat, including heme iron, advanced glycation end products, and nitrites, are thought to mediate the association between meat intake and risk of T2D (6). In our analysis, adjusting for red and processed meat and heme iron attenuated the estimates, although they remained statistically significant, suggesting that they are partial mediators. … In contrast, plant-based sources of protein, such as nuts (8), legumes (9), and whole grains (39), have been associated with a decreased risk of T2D. These foods have healthful nutritional profiles characterized by low glycemic index values and a high content of fiber and micronutrients.
*In a metabolomics study, Wang et al. (40) found strong positive associations between branched chain and aromatic amino acids and incident T2D. These amino acids have also been found to be associated with increased T2D risk (41) and represent the majority of amino acids entering circulation after consumption of red meat (42). In our analysis, adjustment for these amino acids attenuated associations between protein intake and risk of T2D, suggesting that they may be partial mediators.
It probably isn’t just one nutrient. Not just certain amino acids or saturated fat or heme iron or nitrites. Not just fiber or vitamins. It’s probably all of these things acting together. There’s also the higher levels of POPs (persistent organic pollutants) in animal foods that have been shown to raise diabetes risk.
I’ve watched people go from taking metformin to insulin, becrying “the diabetes” as if it was something that happened to them, not something they were causing. Did you see the study in the new issue of Diabetes Care? They put people on very low calorie, low-fat diets and reversed their diabetes. No more meds, no more high blood glucose. Lower cholesterol, blood pressure, triglycerides, plasma insulin too. But it only worked in people who still had some beta cell function (beta cells in the pancreas produce insulin), who only had diabetes for a few years.
I’ve said this for years … a low-fat, plant-food based diet is the best diet to prevent diabetes, heart disease, cancer, arthritis, and other chronic degenerative conditions. I’ll keep on saying it because I think it matters.