BARCELONA, SPAIN and DALLAS, TEXAS-- A new clinical study shows that substituting walnuts for monounsaturated fat in a Mediterranean diet improves, and even restores, endothelial function (the property of arteries to dilate in order to meet an increased demand of blood, for instance due to a physical effort). Walnuts also reduce harmful cell adhesion molecules which are associated with atherosclerosis, commonly known as hardening of the arteries.
These dual effects enhance the circulatory system, therefore aiding in the prevention of heart disease.
Published in today's issue of Circulation: Journal of the American Heart Association, the study concludes that the results provide further support for the inclusion of walnuts in healthy diets. "This is the first time a whole food, not its isolated components, has shown this beneficial effect on vascular health," according to Emilio Ros, M.D., the Hospital Clinic of Barcelona, researcher who directed the study at the setting of the Institute of Biomedical Research August Pi i Sunyer (IDIBAPS). Dr. Ros notes, "Compared with the Mediterranean diet, the walnut diet increased endothelium-dependent vasodilation by 64 percent and
reduced levels of vascular cell adhesion molecule-1 by 20 percent. In addition, as in previous studies, the walnut diet decreased total cholesterol and LDL cholesterol."
Dr. Ros cites the powerful nutrient profile of walnuts as providing this capacity to improve vascular elasticity.
Specifically, he notes that, "Walnuts differ from all other nuts because of their high content of alpha-linolenic acid (ALA), a plant-based omega-3 fatty acid, which may provide additional
anti-atherogenic properties." He also references the amino acid L-arginine, and the gamma-tocopherol form of vitamin-E, both of which walnuts are rich in, as effective in preventing harmful vascular blockage.
"To put it simply, a healthy artery is like an elastic rubber pipe that allows changes in flow, while an artery with impaired endothelial function is like a rigid lead pipe that has a constant flow. The walnut diet in this study actually restored the elasticity of the artery, allowing increased blood flow on
demand," explains Dr. Ros. "Anyone who has risk factors for heart disease, such as smoking, high blood cholesterol, diabetes, hypertension or obesity, is in a situation where the arteries do
not dilate properly when they need to. That's what is called endothelial dysfunction. The patients in our study had high blood cholesterol, a known cause of endothelial dysfunction, and this abnormality was corrected by the walnut diet. The encouraging results of this study provide physicians and patients with a
powerful, yet simple, nutritional tool in their fight against heart disease," he says.
Conducted by the Lipid Clinic at the Hospital Clinic of Barcelona, the study is entitled, "A walnut diet improves endothelial function in hypercholesterolemic subjects: a randomized crossover trial." 21 men and women (ages 25-75) with high cholesterol followed a cholesterol-lowering Mediterranean diet, and a diet of similar energy and fat content in which approximately 1.4-2.3 ounces of walnuts daily (equivalent to
40-65 grams or 8-13 walnuts), based on subjects' total caloric intake, replaced roughly 32 percent of the energy from monounsaturated fat. Participants followed each diet for four weeks.
University of Barcelona is one of the two most productive scientific institutions in Spain according to statistics recently published by the European Union. With regard to scientific output, the Hospital Clinic of Barcelona is among the top 10 leading hospitals in the European Union and is first place among hospitals in Spain.
Co-investigators in this study include Isabel Nunez, MD; Ana Perez-Heras, RD; Merce Serra, RD; Rosa Gilabert, MD; Elena Casals, MD; Ramon Deulofeu, MD.