By promoting clotting and the aggregation of other potential trouble-makers in the bloodstream, inflammation is widely seen as a risk factor for cardiovascular disease, metabolic dysfunctions, certain cancers and brain disorders ranging from depression to dementia. Though its exact role in such diseases is unclear, “it is not an innocent bystander,” said Janice Kiecolt-Glaser, director of Ohio State University’s Institute for Behavioral Medicine Research and the study’s lead author.

So when markers of inflammation are driven up or down by what we eat and how we live, it offers scientists some insights into the mechanisms by which chronic inflammation does damage. And it offers those looking for better health some clear guidance about what to embrace and what to avoid.

In the current study, Kiecolt-Glaser and her team put 58 healthy women (with an average age of 53) through a battery of tests before and after they were assigned to one of two groups on two separate visits: After a day in which all participants got the same meals to eat at home, the women arrived to the study site and were assigned to get one of two meals, both of them a high-calorie (930 calories), high-fat (60 grams) breakfast of eggs, turkey sausage, biscuits and gravy. One group’s breakfast was made the typical fast-food way, prepared in butter and very high in saturated fats. The second group of women got the same breakfast prepared with sunflower oil: Though still a dense, filling meal, the second group’s breakfast leaned more heavily on the kinds of unsaturated fats that are a central component of what’s called a “Mediterranean diet.”