That’s according to a study published Thursday in The American Journal of Clinical Nutrition. Researchers from the T.H. Chan School of Public Medicine at Harvard University analyzed health data collected from nearly 220,000 participants over 36 years. During that time, nearly 10% of participants developed type 2 diabetes.

When researchers reviewed participants’ eating habits, they found that those who ate the most red meat had a 62% higher risk of developing type 2 diabetes when compared to those who ate the least amount of red meat. 

Beyond one serving of red meat per week, each additional serving of processed red meat came with a 46% increased risk of developing diabetes, and each serving of unprocessed red meat an additional 24% greater risk, researchers found.

“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 wellbeing,” Dr. Walter Willett, a professor of epidemiology and nutrition at Harvard, said in a news release about the study.

Other studies—but not all—have come to similar conclusions. A 2013 study from Harvard and the Cleveland Clinic found that increased red meat consumption over time elevates one’s risk of developing type 2 diabetes—in part because it leads to an increase in body weight.

But there may be more to the risk than the meat itself. A 2018 Harvard study found that people who frequently eat red meat, chicken, or fish cooked over an open flame or high temperature—as you would when you barbecue—had 1.5 times the risk of developing type 2 diabetes. 

That may be because cooking meats at high heat can produce chemicals like heterocyclic aromatic amines, polycyclic aromatic hydrocarbons, and advanced glycation end products—all of which are known carcinogens, increase inflammation, or reduce insulin sensitivity, according to the authors of the 2018 article.

Protein-packed substitutes for red meat

If you’re wondering what to eat instead, there are plenty of options.

Everyone should aim to eat 50 grams of protein per day, based on a 2,000 calorie diet, according to the U.S. Food and Drug Administration. But the agency encourages people to vary the sources of their protein, and to choose a variety of the following:

• Beans
• Peas
• Lentils
• Eggs
• Low- or no-fat dairy products
• Unsalted nuts and seeds
• Soy products 
• Lean meats
• Poultry
• Seafood

The good news for people: Substituting one daily serving of red meat with nuts or legumes should lower your type 2 diabetes risk by 30%. Consuming protein from dairy sources instead results in a 22% reduced risk, authors of the latest study found.

And for the planet: Choosing healthy plant protein sources instead of red meat reduces greenhouse gas emissions and slows climate change, researchers added.