Researchers who tracked the diets of 93,600 women found that those who ate more than three servings of strawberries and blueberries per week were 32% less likely to have a heart attack during the 18-year study—even those with a history of high blood pressure. The source of berry power: anthocyanins, flavonoids that give the fruits their bright colors. “They seem to make arteries and blood vessels more flexible, which lowers blood pressure,” says study coauthor Eric Rimm, ScD. Aim for three 1/2-cup servings of fresh or frozen berries weekly. More from Prevention: The 25 Best Foods For Your Heart