Flavonoids, a natural nutrient in cocoa, improve blood flow in the brain, which helps boost cognitive function. Plus dark chocolate contains a tannin called procyanidin, which is also found in red wine, that can keep your arteries flexible and your blood pressure low. It helps on the outside, too. In a study from the Journal of Nutrition, women who drank cocoa fortified with a chocolate bar’s worth of flavonols had better skin texture and stronger resistance to UV rays than those who drank significantly fewer flavonols. Indulge in 1 ounce a day to get all the benefits, says dietitian Sari Greaves of New York Presbyterian Hospital–Cornell.