A look at the interplay between diet and disease shows that when it comes to protecting health, avoiding processed meats may help. According to a review published in Circulation, one serving per day ups the odds of developing diabetes by 19% and heart disease by 42%.

The popular message to eat less red meat for heart disease and diabetes prevention hasn’t been consistently backed by research, and not all of the studies have looked at the types of meat that people were eating. So, what if some of the perceived risk actually stems from the way the meats are prepared, rather than the meat itself?

A team of researchers from the Harvard School of Public Health reviewed 20 different studies, looking for clues about the connection between red and processed meat consumption and the risk of developing heart disease, diabetes, and stroke.

For the purposes of the review, red meat was defined as unprocessed meat from beef, hamburgers, lamb, pork, and game.

One serving of red meat was 100 grams (about 3.5 ounces).

Processed meats included any meat preserved by smoking, curing, salting, or adding chemical preservatives, such as bacon, salami, sausages, hot dogs, and processed deli meats, including some poultry.

One serving of processed meat was 50 grams (about 1.8 ounces).