The Mediterranean diet refers to a way of eating that has its roots in the traditional foods of Greece and southern Italy. The diet is rich in fatty fish, olive oil, vegetables, whole grains, and nuts and legumes, but light on red meats and dairy products. Researchers who studied about 15,000 Greek women for 10 years found that postmenopausal women who’d followed the Mediterranean diet most closely were 22 percent less likely to develop breast cancer than those who strayed the farthest from this way of eating.