Studies have already shown that walnuts enhance endothelial function and protect the cardiovascular system, but now a new trial indicates they may be even more beneficial than olive oil. A team of researchers from the University of Barcelona randomized 24 nonsmoking, middle-aged, healthy adults to two groups of 12 for a crossover study. Each volunteer was provided with two high-fat meals, eaten under supervision one week apart. The meals were identical, consisting of a salami-and-cheese sandwich on white bread and full-fat yogurt. For one meal, the researchers added about five teaspoons (25 mL) of olive oil. For the other, they added 40 g of walnuts, or about eight shelled nuts.

Both the olive oil and the walnuts helped to lessen the sudden onset of inflammation and oxidation in the arteries. But unlike olive oil, walnuts, which are high in antioxidants, also helped to preserve the elasticity and flexibility of the arteries, regardless of the subject’s cholesterol levels (half the volunteers had moderately high LDL and triglyceride levels).

“Each time we eat a high-fat meal, the fat molecules trigger an inflammatory reaction that reduces arterial elasticity,” explains lead researcher Emilio Ros, MD, PhD. “Over time, this repeated damage is thought to contribute to atherosclerosis and heart disease” (J Am Coll Cardiol. 2006;48:1666-1671).

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But Dr. Ros warns that “people would get the wrong message if they think they can continue eating unhealthy fats provided they add walnuts. Instead, they should consider making walnuts part of a diet that limits saturated fats.”