To get a clearer sense of people’s intake of fat from dairy and heart disease risk, Warensjo and her team measured blood levels of two biomarkers of milk fat in 444 heart attack patients and 556 healthy controls. The substances, pentadecanoic acid and heptadecanoic acid, indicate how much dairy fat a person has been eating.

The researchers found that people with the highest levels of milk fat biomarkers, suggesting they consumed the most dairy fat, were actually at lower risk of heart attack; for women, the risk was reduced by 26 percent, while for men risk was 9 percent lower.

Based on the American Heart Association’s Heart Attack Risk Calculator, a normal-weight 60-year-old man with no risk factors for heart disease (such as smoking or diabetes) has a 6 percent risk of dying over the next 10 years; the current study suggests, therefore, that if this hypothetical man ate lots of dairy food, he would reduce his risk by about half a percent. For a woman, or someone at higher risk of a heart attack, the benefit would be larger.

Dairy foods contain a number of potentially beneficial substances, such as calcium, vitamin D, and potassium, Warensjo and her team note. They have also been shown to increase people’s levels of “good” HDL cholesterol.

“The exact mechanism behind these associations cannot be deduced from the present study, but the range of bioactive components present in the food matrix of milk products as well as associated lifestyle factors may all have contributed to the observed associations,” the researchers conclude.