At random, the researchers assigned half of the study patients to eat a cholesterol-lowering Mediterranean diet, which limited red meat and eggs, emphasized vegetables and fish, and used olive oil for cooking. It allowed no nuts. The other half of the subjects ate a diet containing similar amounts of calories and fat, but walnuts made up 35% of the fat content. After 6 weeks, the subjects switched to the other type of diet for another 6 weeks. The researchers measured cholesterol levels at the beginning of the study and again after 6 weeks of each type of diet.