Pesticide and Environmental Update
Antioxidant
Effects from Eating Almonds
Eating almonds significantly decreased
levels of two biomarkers for oxidative stress in a group of 27 male and
female volunteers with elevated cholesterol. The study was conducted by
scientists funded by the Agricultural Research Service, the Almond Board
of California, and the Canada Research Chair Endowment.
Coauthor Jeffrey Blumberg is director of
the Antioxidants Research Laboratory at the Jean Mayer USDA Human
Nutrition Research Center on Aging (HNRCA) at Tufts University in Boston,
Mass. He and colleagues reported the findings from this study in the
Journal of Nutrition.
HNRCA scientists analyzed blood and urine
samples from the subjects who had consumed three different dietary
treatments, consisting of the same amount of calories each, for one month.
The study was a cross-over, randomized clinical trial, so each subject
received each treatment in random order.
Treatments consisted of a "full
dose" of almonds, defined as 73 grams daily (about 2.5 ounces), a
"half-dose" of almonds plus a half-dose of muffins, and a
full-dose of muffins as a control. The subjects consumed a low-fat
background diet and were counseled on strategies to maintain weight and to
consistently follow their usual exercise routines throughout each test
phase.
The researchers wanted to investigate
possible antioxidant effects from eating almonds.
The team found that when the volunteers ate
the full dose of almonds, their concentration of two biomarkers of
oxidative stress--plasma malondialdehyde (MDA) and urinary isoprostanes--were
significantly lowered. MDA decreased by nearly 19 percent compared to the
start of the study in the full-dose almond group. Isoprostane decreased by
27 percent in both the almond groups when compared to the control period,
suggesting a possible threshold effect for that biomarker.
While this study helps to show the
antioxidant benefit of eating almonds, further research is needed to shed
light on the individual contributions of vitamin E and polyphenolic
constituents, such as flavonoids, found in almonds and other tree nuts.
The study did not demonstrate a minimum amount of dietary almonds that
would result in a biological effect.
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