We recently learned that one high-saturated-fat meal may reduce HDL (good) cholesterol's ability to protect our arteries. A new study published in the October 17th issue of the Journal of American College of Cardiology, and partly funded by the California Walnut Commission, suggests that a handful of walnuts can help protect our arteries against the "shock" of a high-saturated-fat meal.

This small study comprised 24 non-smoking, normal-weight adults. Half the sample had moderately high cholesterol but were not on cholesterol-lowering medication; the other half had normal cholesterol levels. All the volunteers were given two meals, one week apart, each consisting of a salami-and-cheese sandwich on white bread and a full-fat yogurt. For one meal, half the volunteers were given eight shelled walnuts with their sandwich and yogurt, while the other half were given five teaspoons of olive oil. For the second meal, those who were given walnuts the first time were given olive oil, and vice versa.

Both the olive oil and the walnuts reduced the sudden onset of inflammation and oxidation in the participants’ arteries after eating the high-fat meal. But the arteries of those eating the walnuts stayed more flexible than those consuming the olive oil—regardless of the volunteers’ cholesterol level. Researchers attribute the difference to the fact that walnuts contain alpha-linolenic acid, a plant-based omega-3 fatty acid. Among other things, omega-3 fatty acids help boost artery-clearing HDL cholesterol and reduce inflammation. Walnuts also contain L-Arginine, an amino acid that the body uses to produce nitric oxide, which helps relax the arteries.

The results of the study are interesting because olive oil is seen as the key component of the much-touted heart-healthy Mediterranean diet. But this isn’t the first time walnuts have been found to be more protective than olive oil. Another study conducted by the same research team, which was published in the April 2004 issue of the journal Circulation, found that a group of adults with high cholesterol fared better on a modified Mediterranean diet where one-third of the monounsaturated fat component—including olives and olive oil—was replaced by polyunsaturated-fat-rich walnuts. Not only did the modified diet reduce total and bad cholesterol, it also increased the elasticity of their arteries. Again, this study was partly funded by the California Walnut Commission.

More on Heart-Healthy Fats

• Good Fats, Bad Fats
• Cholesterol-Lowering Benefits of Walnuts by About’s Guide to Cholesterol
• Walnuts in a Heart-Healthy Diet by About’s Guide to Heart Disease / Cardiology