Eating just two servings of red meat a week might increase the risk of developing Type 2 diabetes, and the risk increases with greater consumption, according to a new study at the Harvard T.H. Chan School of Public Health.
Researchers also found that replacing red meat with healthy plant-based protein sources, such as nuts and legumes, or modest amounts of dairy foods, was associated with reduced risk of Type 2 diabetes.
“The association between red meat and Type 2 diabetes has been observed in different populations worldwide,” the study’s first author, Xiao Gu, a postdoctoral research fellow at Harvard, told CNN. “We keep strengthening existing evidence with improved data and techniques. I hope our study could settle the debate regarding whether we should limit red meat intake for health concerns or not.”
The study was published on Thursday in The American Journal of Clinical Nutrition.
“Our findings strongly support dietary guidelines that recommend limiting the consumption of red meat, and this applies to both processed and unprocessed red meat,” Gu said.
While previous studies have found a link between red meat consumption and Type 2 diabetes risk, this study, which analyzed a large number of Type 2 diabetes cases among participants being followed for an extended period of years, adds a greater level of certainty about the association.
Researchers analyzed health data from 216,695 participants — 81% women — from the Nurses’ Health Study (NHS), NHS II, and Health Professionals Follow-up Study. Diet was assessed with food frequency questionnaires every two to four years, for up to 36 years. During that time, more than 22,000 participants developed Type 2 diabetes.
About 462 million people worldwide are affected by Type 2 diabetes, a rate that has been rapidly increasing, the authors said.
Study participants who ate the most red meat had a 62% higher risk of developing Type 2 diabetes compared to those who ate the least, according to the study. Every additional daily serving of processed red meat was associated with a 46% greater risk of developing Type 2 diabetes and every additional daily serving of unprocessed red meat was associated with a 24% greater risk.
The researchers also estimated the potential effects of substituting one daily serving of red meat for another protein source. They found that substituting a serving of nuts and legumes was associated with a 30% lower risk of Type 2 diabetes, and substituting a serving of dairy products was associated with a 22% lower risk.
“Given our findings and previous work by others, a limit of about one serving per week of red meat would be reasonable for people wishing to optimize their health and well-being,” senior author Walter Willett, a Harvard professor of epidemiology and nutrition, said in a press release.
Per NPR, “It’s difficult to unravel whether the meat itself or some constituent of the meat may explain the increased risk of diabetes. Another possible explanation is that people who consume a lot of red meat may have other things in common that could drive up their risk. For instance, excess body weight is a key risk factor for developing Type 2 diabetes.”
Participants in the study who ate high amounts of red meat also had higher body mass indexes. They consumed more calories and were less physically active compared with those who ate the least red meat. Researchers used statistical methods to adjust for confounding variables.
“We found that about half of the excess risk with red meat consumption was explained by excess body weight but there was still an increased risk (of developing diabetes) even after taking into account body weight,” Willett said, according to NPR.
Willett pointed to several potential factors that may explain the remainder of the risk. “There’s evidence that heme iron in red meat may damage the cells in the pancreas that secrete insulin,” he said.
People tend to think of red meat as a risk factor for heart disease due to the concentration of saturated fat, but Willett said the type of fat that people consume may also drive up the risk of diabetes. U.S. dietary guidelines recommend limiting saturated fat to 10% or less of daily calories. Willett recommends swapping servings of red meat with plant-based proteins such as nuts and soy, which have a lot of polyunsaturated fat, as a way to protect against disease, per NPR.