Researchers report a strong correlation between walnut-rich diet and lowered risk of heart disease.
The study due for publication in the June 1, 2013 edition of the Journal of Nutrition and currently online indicates that intake of a diet rich in whole walnuts or their extracted oil translates into a lowered risk of heart disease.
In a controlled trial, researchers led by Penny Kris-Etherton, Ph.D., distinguished professor of nutrition of Penn State, studied 15 participants with high cholesterol by assigning them to one of the four treatments: 85 grams of whole walnut, 6 grams of skin, 34 grams of defatted nutmeat or 51 grams of oil. The researchers then checked for elevation in blood lipid levels, endothelial function, and oxidative stress of the participants both before the treatment and after, at different durations ranging from 30 minutes, one hour, two hours, four hours and six hours. They assessed cholesterol efflux in the patients on whole walnut treatment.
The results showed that the "walnut skins lowered the reactive hyperemia index (RHI) compared with baseline such that a difference persisted between the skin and oil treatments". Reactive hyperemia refers to the short increase in organ blood flow that occurs following a brief period of restricted supply when the heart becomes starved of oxygen.
The study results explain the the cardiovascular benefits of walnuts based on two novel mechanisms: "walnut oil favorably affected endothelial function and whole walnuts increased cholesterol efflux."
"We already know that eating walnuts in a heart-healthy diet can lower blood cholesterol levels," said Dr. Kris-Etherton. "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," according to the university news release.
They noticed that one-time consumption of the walnut oil affected vascular health. Also, consumption of the whole walnut aided HDL (good cholesterol) function more efficiently, in carrying and eliminating surplus cholesterol from the body.
"Our study showed that the oil found in walnuts can maintain 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, graduate student in nutritional sciences, Penn State, in a press statement. "The walnut oil was particularly good at preserving the function of endothelial cells, which play an important role in cardiovascular health."
The researchers attribute the health benefits of walnuts to alphap-linolenic acid, gamma tocopherol and phytosterols.
