Nuts may improve cardiovascular health
If you are what you eat, and if you eat nuts….well, you see where I’m going with this. But when you regularly include nuts in your diet, you’re anything but nuts, because they deliver an abundance of healthy nutrients. In fact, new studies show how key components in two types of nuts help support cardiovascular health.
Secret in the sweet pecan
More than four years ago, in an e-Alert that addressed the different forms of vitamin E, HSI Panelist Allan Spreen, M.D., noted that gamma tocopherol is the vitamin’s key element that suppresses oxidation and prevents free radical damage.
Pecans, it turns out, are packed with gamma tocopherol.
In a study from Loma Linda University in California, researchers randomly divided 24 subjects (ages ranged from 25 to 55) into two groups. One group followed the American Heart Association Step I diet (which restricts fat to no more than 30 percent of total caloric intake), and the second group followed a modified version of the diet in which pecans accounted for 20 percent of the calories. After four weeks, each group crossed over to the opposite diet for an additional four weeks.
Blood samples taken before the diets began and throughout the study period revealed two significant results:
- Overall gamma tocopherol concentrations increased by more than 10 percent when subjects were on the pecan diet
- Oxidation of lipids was reduced by more than seven percent by the pecan diet compared to the AHA Step I diet
When blood lipids are oxidized (particularly LDL cholesterol), they’re more likely to contribute to cardiovascular problems.
Bring the walnuts
The second nut study examined walnuts, which are rich in alpha-linolenic acid (a precursor of omega-3 fatty acids), which has been shown to enhance blood vessel resiliency.
Researchers at the Universitat Autonoma de Barcelona recruited 12 subjects with high cholesterol levels and 12 subjects with normal cholesterol levels. Each subject ate a high-fat meal containing 80 grams of fat, with 35 percent saturated fat. Half of the meals included 25 grams of olive oil, and the other half included 40 grams of walnuts. After a one-week washout period, the meals were repeated, with the olive oil group switching over to the walnut meal and vice versa.
Blood samples taken before and after the two meals showed that flow-mediated dilation (a blood vessel resiliency measure) was improved after the walnut meal, but not after the olive oil meal. Concentrations of oxidized LDL cholesterol decreased slightly after both meals.
One of the authors of the study, Emilio Ros, M.D., told FoodNavigator that walnuts are often overlooked as an important element of the Mediterranean diet. He also noted that walnuts contain L-arginine, an anti-inflammatory amino acid that has been shown to improve artery function.
Nudging evidence along
Three years ago, the FDA announced that the producers of some nuts (pecans, walnuts, almonds, pistachios, and hazelnuts) and nut products would be allowed to make this claim: “Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”
I don’t suppose these two small studies will nudge the evidence squarely into the “proven” zone, but we’re clearly moving in that direction.
“A Pecan-Enriched Diet Increases Gamma-Tocopherol/Cholesterol and Decreases Thiobarbituric Acid Reactive Substances in Plasma of Adults” Nutrition Research, Vol. 26, No. 8, August 2006, sciencedirect.com
“Vitamin E in Pecans May Reduce LDL Oxidation” Clarisse Douaud, NutraIngredients, 9/29/06, nutraingredients.com
“Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function” Journal of the American College of Cardiology, Vol. 48, No. 8, 10/17/06, content.onlinejacc.org
“ALA-Rich Walnuts Could Protect Arteries After High-Fat Meal” Stephen Daniells, FoodNavigator, 10/11/06, foodnavigator.com