A diet high in protein may be healthy, but the type of protein you eat could determine your risk factors for having a stroke. New research indicates red meat raises those risks, while poultry lowers them.

In a 20-year study, Dr. Frank Hu, a professor at the Harvard School of Public Health, and his colleagues collected data from two massive health surveys that tracked tens of thousands of men and women from roughly middle age to their senior and elderly years. During the study period, 1,400 men and more than 2,600 women had a stroke.

To ascertain how different types of dietary protein could affect stroke risk, researchers divided up the study participants based on how much red meat, poultry, fish, dairy and other sources of protein they typically ate every day.

They found men who ate more than two servings of red meat each day — a serving being defined as four to six ounces of beef or a hamburger patty — had a 28 percent increased risk of stroke compared to men who averaged about a third of a serving of red meat each day, while women who ate nearly two servings of red meat a day had a 19 percent higher risk of stroke than women who ate less than half a serving each day.

It was also learned that swapping in one serving a day of poultry actually lowered stroke risk by 27 percent. A serving of nuts or fish was linked to a 17 percent drop in risk, and a serving of dairy dropped the risk by 10 to 11 percent.

The researchers didn’t prove that beef itself is to blame for the increased number of strokes, but Dr. Adam Bernstein, the lead author of the study and a researcher at the Cleveland Clinic, said it could be that the fat and iron in red meat play a role.