Although high in total fat content, walnuts are often considered to be heart-healthy because they are rich in omega-3 fatty acids and low in saturated fat. In highly controlled clinical feeding trials, walnuts have been shown to improve cholesterol levels in humans in the short term. Until recently, however, it was not known whether the same effects occur in less controlled situations and over longer periods of time.
A recent study investigated the effects of walnut consumption in 87 free-living adults over the period of one year (1). Half of the participants were given walnuts to eat every day, providing 12% of their energy needs, and they were asked not to make any other diet or exercise changes. The other half continued their usual diet, without supplemental walnuts. After six months, the groups switched treatments for another six months. Blood samples were collected from participants at five time points during the study, for measurement of total cholesterol, LDL cholesterol, HDL cholesterol, LDL:HDL ratio, and triglycerides. The researchers found that daily walnut consumption resulted in significant reductions in total cholesterol and triglyceride levels. These favorable effects were greatest among individuals who had the highest cholesterol levels at the beginning of the study.
This study shows that the addition of walnuts to one’s regular diet, even without any dietary advice, is one way to improve cholesterol and triglyceride levels, particularly among people with elevated cholesterol. These results are consistent with previous studies connecting walnut consumption with improved cardiovascular health.
Torabian S, Haddad E, Cordero-MacIntyre Z, Tanzman J, Fernandez ML, Sabate J. Long-term walnut supplementation without dietary advice induces favorable serum lipid changes in free-living individuals. Eu J Clin Nutr 2010;64:274-9.