Ask the doctor
Q: I've read a lot lately about nuts and how they prevent heart disease. How much should I eat, and are some nuts healthier than others?
A: Nuts contain high amounts of polyunsaturated fat and are a staple in the popular Mediterranean diet. Commonly studied nuts include walnuts and almonds, which have been shown in short-term studies to lower cholesterol. In the PREDIMED trial, a Mediterranean diet supplemented with 30 grams of nuts daily reduced the risk of heart disease. Thirty grams of nuts is equal to about 20 almonds or 10 walnuts. In other studies that showed health benefits from nuts, the frequency of consumption was recorded, not the amount. Daily consumption appeared to be best.
There is a caveat to the claim of health benefits from nuts. Many of the supporting studies were observational in nature, demonstrating an association between nuts and better health outcomes but not a cause-and-effect relationship. It could be that individuals with a healthy lifestyle (in whatever way) also were the ones who tend to eat more nuts. Another dietary factor or exercise habits could be the main reason for the association with good health.
Regardless of your preferred nut, there are some cautions. Nuts are high in calories (185 calories per ounce), so don't eat too many. Some people are allergic to nuts, and for them, even small amounts could be dangerous. For most people, adding a serving of nuts to your usual daily meals (and eliminating a food with low health value) is a good idea.
--William Kormos, M.D.
Editor in Chief, Harvard Men's Health Watch