Walnuts have long been hailed as a heart-healthy food because eating them can lower cholesterol levels. But new research has found consumption of whole walnuts or their extracted oil can also cut cardiovascular risk in ways that are independent of — and complementary to — their cholesterol-lowering properties.
 

The findings — by a team of nutritional specialists from Penn State, Tufts University, and University of Pennsylvania researchers — suggest even a single consumption of the oil component in walnuts can boost blood-vessel function. In addition, whole walnuts make HDL — the “good” cholesterol — perform more effectively in transporting and removing excess “bad” cholesterol from the body.
 

"We already know that eating walnuts in a heart-healthy diet can lower blood cholesterol levels," said Penny Kris-Etherton, a professor of nutrition at Penn State. "But, until now, we did not know what component of the walnut was providing this benefit. Now we understand additional ways in which whole walnuts and their oil components can improve heart health."
 

For the study, the researchers gave 15 participants with elevated blood cholesterol one of four treatments — 85 grams of whole walnuts, 6 grams of walnut skins, 34 grams of defatted nutmeat, or 51 grams of oil. The team evaluated the biochemical and physiological responses in the participants before the treatments were administered and again 30 minutes, one hour, two hours, four hours and six hours after administering each of the treatments.
 

The results, published online in Journal of Nutrition, showed the oil found in walnuts can help maintain healthy blood vessel function after a meal — “ which is very important given that blood vessel integrity is often compromised in individuals with cardiovascular disease," said Claire Berryman, a graduate student in nutritional sciencesat Penn State.

"The walnut oil was particularly good at preserving the function of endothelial cells, which play an important role in cardiovascular health."

According to the researchers, walnuts contain alpha-linolenic acid, gamma-tocopherol, and phytosterols, which may explain the positive effects of the walnut oil treatment.
 

"Implications of this finding could mean improved dietary strategies to fight heart disease," said Berryman. "The science around HDL functionality is very new, so to see improvements in this outcome with the consumption of whole walnuts is promising and worth investigating further.
 

"Our study indicates that simple dietary changes, such as incorporating walnuts and/or their oil in a heart healthy diet, may reduce the risk of heart disease."