
Too much red meat consumption is associated with a 50% increased risk of type 2 diabetes, according to a new study. Processed meats like bacon and hot dogs are linked to an even higher risk.
Researchers tracked the eating habits of over 200,000 individuals participating in long-term health studies spanning 36 years and found that those who regularly consumed a large amount of red meat (more than one serving per day) had a significantly higher risk of developing type 2 diabetes.
"When we looked at women and men who consumed more red meat compared to the least, we found about a 50% increase in risk," says study author Dr. Walter Willett from the T.H. Chan School of Public Health at Harvard. The results were published in the American Journal of Clinical Nutrition.
It is challenging to determine whether the meat itself or some of its components explain the increased risk of diabetes. Another possible explanation is that people who consume a lot of red meat may have other common traits that can elevate their risk. For instance, excess body weight is a key risk factor for type 2 diabetes.
It turned out that study participants who consumed a significant amount of red meat also had a higher body mass index. They consumed more calories and were less physically active compared to those who consumed the least red meat. Researchers used statistical methods to adjust for intervening variables. "We found that about half of the excess risk associated with red meat consumption could be explained by excess body weight," says Willett, "but there is still an elevated risk of diabetes even after taking body weight into account."
Willett points to several potential factors that could explain the remaining risk. "There is evidence that heme iron in red meat can damage insulin-secreting cells in the pancreas," he says. Other data suggest that excessive red meat consumption can increase insulin resistance and inflammation. Scientists at Tufts University are studying how metabolites associated with red meat consumption, such as TMAO, can trigger inflammatory processes.
Research by Dr. Suzanne de la Monte at Brown University has shown that nitrosamines, compounds formed when nitrites are added to food, may contribute to insulin-resistant diseases, including diabetes. Nitrates and nitrites are added to meat during processing or for preservation. "Then, when they are heated and consumed, nitrates and nitrites are converted into nitrosamines," explains de la Monte. This year, the European Food Safety Authority determined that the level of nitrosamine exposure in food poses a health risk. Processed meat typically has an even higher level of nitrosamines.
People tend to think of red meat as a risk factor for cardiovascular diseases due to the concentration of saturated fats, but Willett says that the type of fat people consume can also increase the risk of diabetes. U.S. dietary recommendations suggest limiting saturated fat to 10% or less of daily calories. As a way to protect against diseases, Willett recommends replacing red meat portions with plant-based proteins like nuts and soy, which are rich in polyunsaturated fats.
He warns that substituting red meat with products known to spike blood sugar levels, such as sweets and highly processed snacks, as well as refined starches like white bread, is not a healthy strategy. "This will not reduce the risk of diabetes," he says.
Given that only about 4% of people in the U.S. consider themselves vegetarians and only 1% are vegans, it's unrealistic to think that people will completely give up red meat. Tara Shrout Allen, a physician from the University of California, San Diego, advises her patients on the benefits of reducing red meat consumption. "I certainly encourage them to cut back from their baseline," Allen says.
So, how much red meat is safe to consume? U.S. dietary recommendations do not specify an amount, but a recent review of observational studies suggests that it is reasonable to limit daily consumption of unprocessed red meat to 50–100 grams, which is no more than 3.5 ounces per day, to prevent high blood pressure and cardiovascular diseases. Willett's recommendation goes even further. "Limiting to about one serving of red meat per week would be a reasonable approach for those looking to improve their health and well-being," he says.
Considering the wealth of data linking excessive red meat consumption to increased risk of cardiovascular diseases and cancer, Christopher Gardner, a nutrition scientist from Stanford University, notes that "recommendations to limit red meat consumption, especially processed red meat, have been made by many national and global health organizations."
Criticism has long been voiced regarding large epidemiological studies like this new one, which cannot establish a cause-and-effect relationship between red meat consumption and disease onset. However, it appears to be the best evidence available to researchers."