In last week's edition of Circulation, Spanish investigators report that adding walnuts to a Mediterranean-type diet improves the function of blood vessels.
Earlier studies have shown that several types of nuts reduce LDL cholesterol levels, and the FDA has issued statements supporting the use of nuts in a heart healthy diet. The Spanish investigators, noting that walnuts contain high levels of antioxidants, L-arginine, and alpha-linoleic acid - substances that themselves can help prevent hardening of the arteries and can increase the dilation of blood vessels - conducted a study to measure the effect of walnuts on blood vessels.
They randomized 21 individuals who had high cholesterol levels to a typical Mediterranean diet, or to a similar diet in which walnuts were substituted for olive oil. They found that a diet enriched in walnuts significantly improved measures of vascular reactivity, a finding associated with improved cardiovascular health. They concluded that adding nuts to the diet - in particular, walnuts - can improve cardiovascular health over and above the improvement that would be predicted from cholesterol-lowering alone.
The FDA has already given its blessing to the advertising of the cardiac benefits of walnuts, almonds, pecans, pistachios, hazel nuts, and peanuts. The current study suggests (though it does not prove) that walnuts may have unique properties that render them more helpful than other varieties of nuts.
