While the heart health potential of walnuts has been reported before, it was not previously known how individual walnut components contribute to these effects.
Consuming the whole walnut was associated with a 3.3% increase in cholesterol efflux, while walnut oil favorably affected endothelial function, according to new data from scientists from The Pennsylvania State University, Tufts University, and The Children’s Hospital of Philadelphia
“This study is the first to our knowledge to report increased ex vivo cholesterol efflux following postprandial consumption of whole walnuts,” they wrote. “Cholesterol efflux is an important antiatherogenic step in the reverse cholesterol transport pathway and is a novel measure of HDL functionality.”
Nut science in a nutshell
The study enhances our understanding of the potential heart health benefits of walnuts, with previous studies indicating that walnuts may reduce the risk of coronary heart disease (American Journal of Clinical Nutrition, 2009, Vol. 89, pp. 1657S-1663S), and the addition of nut-containing foods to the diet at the expense of foods full of saturated fats could reduce cholesterol levels by 6% (Journal of Nutrition, Vol. 138, pp. 761-767).
For the new study, the researchers assessed the effect of whole walnuts, separated nut skins, de-fatted nutmeat, and nut oil in 15 people with mildly elevated cholesterol levels.
Volunteers were randomly assigned to consume 85 grams of whole walnuts, 5.6 grams of nut skins, 34 grams of the nutmeat, or 51 grams of the oil in a crossover trial.
Results showed that consumption of the skins was associated with a decrease in endothelial function, while the oil maintained endothelial function after the meal.
“Walnuts are a rich source of ALA (about 13% of total lipids) and g-tocopherol (20 mg/100 g) and contain phytosterols (164 mg/ 100 g), which may explain the positive effects of the walnut oil treatment,” they explained.
Additional testing using cell cultures indicated that the whole walnut increased cholesterol efflux by 3.3%, compared with baseline values.
“We showed that acute consumption of walnut oil favorably affects endothelial function compared with whole walnuts and walnut skins,” wrote the researchers. “We also demonstrated novel effects of whole walnuts on reverse cholesterol transport.
“Therefore, frequent consumption of walnuts and/or walnut oil (which typically is how walnut products are consumed) may improve cardiovascular risk via mechanisms that extend beyond their established cholesterol-lowering action.”
Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/jn.112.170993
“Acute Consumption of Walnuts and Walnut Components Differentially Affect Postprandial Lipemia, Endothelial Function, Oxidative Stress, and Cholesterol Efflux in Humans with Mild Hypercholesterolemia”
Authors: C. E. Berryman, J. A. Grieger, S. G. West, C-Y. O. Chen, J. B. Blumberg, G. H. Rothblat, S. Sankaranarayanan, P. M. Kris-Etherton