The Mediterranean diet is well-known as a key ingredient in a healthy life. But researchers have been unsure why it’s so beneficial both to body and mind. The diet has widely been shown to reduce the risk for cognitive decline and Alzheimer’s disease, particularly when coupled with exercise. Now researchers are finding that its mechanism may be through the tiny blood vessels of the brain.

Researchers quizzed almost 1,000 healthy seniors about their diets over the years, and ranked them in how closely the followed the Mediterranean diet, which is high in fruits, veggies, whole grains, fish, olive oil, nuts, and beans, and low in red meat, refined grains, sugar, and high-fat dairy. A little red wine is often part of the diet, but in moderation.

The people who stuck closely to the Mediterranean diet had less damage the brain’s blood vessels than people who followed it less closely.

Participants underwent MRI scans to determine the health of the small blood vessels that serve the brain tissue. This “white matter hyperintensity volume” is a known marker of chronic damage to the blood vessels.

The people who stuck closely to the Mediterranean diet had less damage to the brain’s blood vessels than people who followed it less closely. This connection was found even after researchers pulled other variables out of the equation, like blood pressure, cholesterol, and smoking.

One component of the diet stood out: the ratio of monosaturated fats to saturated fats the participants ate. The higher the ratio of mononunsaturated to saturated fats, the better the blood vessel health. The study points to a mechanism through which the Mediterranean diet could exert its effects. Nevertheless, there is likely more at play than monosaturated fats alone, like the amount of antioxidants or other phytochemicals consumed with the diet, or other factors. Even though researchers are still fleshing out exactly how the Mediterranean diet works, one thing we know for sure is that it works, in many areas of our health.

The study was carried out at Columbia University Medical Center, and published in the Archives of Neurology.