Sept. 8, 2004 -- Eating more bacon and red meat than ever? You may be increasing your risk of developing diabetes, a new study shows.
The long-term safety of meat-heavy diets has been questioned, with some studies linking them to kidney damage and colorectal cancer. Now new research points to a link between eating red meat -- especially processed meats -- and type 2 diabetes.
Compared with women who eat less red meat, women who eat red meat frequently have almost a third higher risk of developing type 2 diabetes. Frequently eating bacon, hot dogs, and processed (deli-style) meats was associated with a 43% higher risk of type 2 diabetes in women participating in the large health study.
The new findings are reported by investigators from Harvard Medical School in the September issue of the journal Diabetes Care.
Processing Triggers Insulin Resistance
Researchers followed just more than 37,000 women aged 45 or older for an average of eight years. All of the women completed detailed questionnaires accessing their food choices at study entry, and none had heart disease, cancer, or type 2 diabetes.
At follow-up, 1,560 of the women had developed type 2 diabetes. Even after adjusting for other risks associated with the development of diabetes such as age, weight, and exercise, the researchers continued to find associations between the amount of processed and red meats eaten and the development of type 2 diabetes.
Women who ate five or more servings of red meat a week were found to have a 29% increase in diabetes risk compare with women who ate red meat less than once a week. While those who ate five or more servings of processed meats had a 43% increase in risk compared with women who ate less than a serving of processed meat a week.
Researcher Yiqing Song, MD, and colleagues suggest that the preservatives, additives, and other chemicals used to process meats, including nitrates and nitrites, or chemicals that are formed during processing, could trigger insulin resistance.
Iron may also play a role. Red meat and processed meats are high in iron, and previous studies show a link between high iron levels and type 2 diabetes. Compared with women who got the least iron in their diets in this study, those who got the most were 46% more likely to develop diabetes.
"The underlying mechanism by which consumption of red meat or processed meat influence type 2 diabetes risk are still not well understood and require further investigation," Song and colleagues write.
The Big Picture
Longtime diabetes researcher Frank Hu, MD, PhD, says the new findings are consistent with his earlier research and that of others. Hu has studied the impact of a wide range of different dietary factors on type 2 diabetes risk. Prior studies showed that, among other things, drinking coffee and eating peanut butter may help protect against the disease.
His latest research, published late last month, focused the spotlight on sugary soft drinks. The study showed an 80% increase in diabetes risk among frequent drinkers of sodas sweetened with high-fructose corn syrup.
Hu tells WebMD that refined sugar, processed flour, and hydrogenated fats appear to be biggest culprits in terms of increasing diabetes risk. The most important foods to eat to protect against the disease are nuts and fiber-rich foods such as whole grains, he says.
"The picture is now very clear, but there are still unanswered questions," he says. "Dairy is still controversial. Some studies find it to be protective, but the protection is modest compared with nuts and whole grains."
Hu says foods that trigger rapid blood sugar increases -- those with a high glycemic index -- tend to be the worst in terms of increasing diabetes risk. The low-carb, high-protein diets also eschew high-glycemic index foods, but Hu says that doesn't make them a good choice for lowering diabetes risk.
"These diets are low in fiber and whole grains, which are important sources of phytochemicals, minerals, and antioxidants, he says. "And they are high in saturated fat." Hu is an associate professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.
American Diabetes Association president-elect Robert Rizza, MD, says that while identifying single-food sources associated with diabetes risk is important, weight control and exercise are two proven ways to lower risk.
"The strongest evidence that we have for reducing the risk of type 2 diabetes is staying physically active and maintaining a healthy weight," he says. "While decreasing saturated and trans (hydrogenated) fats and increasing plant-based foods are an important part of the process, we do not want people to lose sight of the significance of an overall healthy lifestyle."