We’ve known that being overweight and obese are important risk factors for type 2 diabetes, but, until recently, not much attention has been paid to the role of specific foods. I discuss this issue in my video below.
A 2013 meta-analysis of all the cohorts looking at the connection between meat and diabetes found a significantly higher risk associated with total meat consumption—especially consumption of processed meat, particularly poultry. But why? There’s a whole list of potential culprits in meat: saturated fat, animal fat, trans fats naturally found in meat, cholesterol, or animal protein.
It could be the heme iron found in meat, which can lead to free radicals and iron-induced oxidative stress that may lead to chronic inflammation and type 2 diabetes, or advanced glycation end (AGE) products, which promote oxidative stress and inflammation. Food analyses show that the highest levels of these so-called glycotoxins are found in meat—particularly roasted, fried, or broiled meat, though any foods from animal sources (and even high fat and protein plant foods such as nuts) exposed to high dry temperatures can be potent sources of these pro-oxidant chemicals.
In another study, researchers fed diabetics glycotoxin-packed foods, like chicken, fish, and eggs, and their inflammatory markers—tumor necrosis factor, C-reactive protein, and vascular adhesion molecules—shot up. “Thus, in diabetes, environmental (dietary) AGEs promote inflammatory mediators, leading to tissue injury.” The good news is that restriction of these kinds of foods may suppress these inflammatory effects. Appropriate measures to limit AGE intake, such as eliminating meat or using only steaming and boiling as methods for cooking it, “may greatly reduce the already heavy burden of these toxins in the diabetic patient.” These glycotoxins may be the missing link between the increased consumption of animal fat and meats and the development of type 2 diabetes.
Since the 2013 meta-analysis was published, another study came out in which approximately 17,000 people were followed for about a dozen years. Researchers found an 8 percent increased risk for every 50 grams of daily meat consumption. Just one quarter of a chicken breast’s worth of meat for the entire day may significantly increase the risk of diabetes. Yes, we know there are many possible culprits: the glycotoxins or trans fat in meat, saturated fat, or the heme iron (which could actually promote the formation of carcinogens called nitrosamines, though they could also just be produced in the cooking process itself).
However, we did learn something new: There also appears to be a greater incidence of diabetes among those who handle meat for a living. Maybe there are some diabetes-causing zoonotic infectious agents—such as viruses—present in fresh cuts of meat, including poultry.
A “crucial factor underlying the diabetes epidemic” may be the overstimulation of the aging enzyme TOR pathway by excess food consumption—but not by the consumption of just any food: Animal proteins not only stimulate the cancer-promoting insulin growth factor-1 but also provide high amounts of leucine, which stimulates TOR activation and appears to contribute to the burning out of the insulin-producing beta cells in the pancreas, contributing to type 2 diabetes. So, it’s not just the high fat and added sugars that are implicated; critical attention must be paid to the daily intake of animal proteins as well.
According to a study, “[i]n general, lower leucine levels are only reached by restriction of animal proteins.” To reach the leucine intake provided by dairy or meat, we’d have to eat 9 pounds of cabbage or 100 apples. That just exemplifies the extreme differences in leucine amounts provided by a more standard diet in comparison with a more plant-based diet.
I reviewed the role endocrine-disrupting industrial pollutants in the food supply may play in a three-part series: Fish and Diabetes, Diabetes and Dioxins, and Pollutants in Salmon and Our Own Fat. Clearly, the standard America diet and lifestyle contribute to the epidemic of diabetes and obesity, but the contribution of these industrial pollutants can no longer be ignored. We now have experimental evidence that exposure to industrial toxins alone induces weight gain and insulin resistance, and, therefore, may be an underappreciated cause of obesity and diabetes. Consider what’s happening to our infants: Obesity in a six-month-old is obviously not related to diet or lack of exercise. They’re now exposed to hundreds of chemicals from their moms, straight through the umbilical cord, some of which may be obesogenic (that is, obesity-generating).
The millions of pounds of chemicals and heavy metals released every year into our environment should make us all stop and think about how we live and the choices we make every day in the foods we eat. A 2014 review of the evidence on pollutants and diabetes noted that we can be exposed through toxic spills, but “most of the human exposure nowadays is from the ingestion of contaminated food as a result of bioaccumulation up the food chain. The main source (around 95%) of [persistent pollutant] intake is through dietary intake of animal fats.”
Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations—2015: Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016: How Not To Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.