Need another reason to cut back on red and processed meats? A new study suggests that a common additive called nitrites in these foods is associated with an increased risk of type 2 diabetes.

For the study, researchers examined the eating habits of more than 104,000 adults who were 43 years old on average and had no history of type 2 diabetes. On the basis of detailed dietary records, scientists calculated how much exposure people had to nitrates and nitrites, chemicals naturally found in whole foods like green leafy vegetables and in additives used to improve the flavor and shelf life of processed meats and other mass-produced foods.

Participants were followed for about seven years, and nearly 1,000 of them developed type 2 diabetes.

People with the most nitrites in their diets from food additives were 53 percent more likely to get a type 2 diabetes diagnosis than participants whose diets contained the smallest amounts of meat and processed foods, the researchers reported January 17 in PLoS Medicine. Exposure to nitrites found naturally in leafy greens and other whole foods was also associated with an increased risk of type 2 diabetes, but the effect was much smaller.

Processed Meats Are the Most Common Source of Added Nitrites

When scientists looked closely at participants’ diets, they found processed meats like ham and sausage were by far the biggest source of food additives containing nitrites, followed by ready-to-eat meals containing processed meats. Combined, these types of foods accounted for 76 percent of nitrates from food additives.

“To reduce the risk of type 2 diabetes, people should eat a variety of unprocessed and minimally processed foods, particularly fruits, vegetables, legumes, nuts, and whole grains — and avoid foods that might increase the risk of type 2 diabetes, such as processed meats, soft drinks, and ultra-processed foods in general,” says Priscila Machado, PhD, a researcher at the Institute for Physical Activity and Nutrition at Deakin University in Australia, who wasn’t involved in the study.

Type 2 diabetes develops when the pancreas can no longer make or use the hormone insulin effectively to convert the sugars in our food into energy. The study wasn’t designed to prove whether or how nitrites might directly cause type 2 diabetes, but scientists do know that nitrites consumed from foods can damage cells in the pancreas responsible for insulin production, says the senior study author, Mathilde Touvier, PhD, a researcher at the French Institute of Health and Medical Research and the Sorbonne Paris Nord University in France.

Leafy Green Vegetables Are Still Part of a Healthy Diet

It’s possible that the study found less risk associated with nitrites in healthy foods like leafy green vegetables because people who eat this way consume an overall healthier diet than people who eat a lot of red and processed meat. There are also lots of nutrients in vegetables, like antioxidants, that protect against diabetes, Dr. Machado says.

Heavily processed meats with lots of food additives containing nitrites may be linked to diabetes in part because they’re part of an overall unhealthy diet, says Gunter Kuhnle, PhD, a nutrition professor at the University of Reading in the United Kingdom who wasn’t involved in the new study.

“In the study, people with high nitrite intake also had other dietary patterns that could be linked with diabetes, such as a high intake of sugars,” Dr. Kuhnle says.

Plant-Based Diets Can Lower Your Risk of Chronic Conditions Like Diabetes

One limitation of the analysis is that scientists relied on people to accurately recall and report on all the foods they ate. Researchers also didn’t objectively measure exposure to nitrates or nitrites by testing foods. Instead, they estimated exposure based on the expected amount in different foods people said they consumed.

Still, the findings add to a growing body of research, described in a January 2020 article in Diabetes Care, linking red and processed meat to an increased risk of type 2 diabetes — with a lower risk for those on a more plant-based diet.

Getting plenty of exercise, maintaining a healthy body weight, abstaining from smoking, and limiting alcohol consumption can also help minimize the risk, according to the U.S. Centers for Disease Control and Prevention.