I wouldn't count on walnuts, or anything else, to protect against unhealthy eating habits, but it is true that Spanish researchers recently reported that eating about eight shelled walnuts worked better than olive oil at protecting arteries from damage that can follow a meal high in saturated fat.
A bit of background: when you eat foods that are high in saturated fat (found in red meat, and full-fat dairy products such as whole milk, cheese, butter, and cream), an inflammatory response occurs which impairs the ability of the arteries to deliver blood to tissues and organs throughout the body. This inflammatory response also promotes formation of artery-clogging plaque that raises risk of heart attack.
In the Spanish study, researchers asked 24 volunteers to eat a salami and cheese sandwich on white bread followed by a serving of high-fat yogurt. Then, they gave half the volunteers eight shelled walnuts and gave the other half five teaspoons of olive oil. When the researchers did ultrasound examinations of the arteries of their participants, they found that those of the group that ate the walnuts remained more flexible and elastic than those of the group that consumed the olive oil.
While both olive oil and walnuts have beneficial effects on arteries after a high fat meal (they reduce inflammation and oxidation), this study showed that only the walnuts maintained flexibility of the arteries. The researchers credited the alpha-linolenic acid (ALA) found in walnuts for this effect (ALA is an omega-3 fatty acid similar to those omega-3 fatty acids found in fish). The study was published in the October 17, 2006 issue of the Journal of the American College of Cardiology.
This study adds to earlier evidence attesting to the health benefits of walnuts. If you buy packaged walnuts, you've probably noticed the label claim stating that eating 1.5 ounces daily, as part of a low-saturated-fat and low-cholesterol diet, and not resulting in increased caloric intake, may reduce the risk of coronary heart disease. The Spanish researchers recommend a Mediterranean diet, which is low in saturated fats and is features high-quality fresh fruits and vegetables, nuts, legumes, unrefined cereals, olive oil, fermented dairy products such as yogurt and natural cheese, and fresh fish as daily staples. The diet doesn't eliminate red meat but limits it to about one meal a month; similarly, poultry, eggs and sweets are permitted but are not for everyday consumption.
Walnuts are definitely good for you, as long as you don't overdo it; like other nuts, they are relatively high in calories. I usually eat a handful a day.
Andrew Weil, M.D.