March 24, 2008 — No matter how pleasant a
meal is, eating causes what’s known as oxidative stress. As we digest
our food, we create sometimes-harmful molecules known as free radicals.
But antioxidants — healthful compounds in fruits and vegetables — can
help by neutralizing the free radicals.
That’s yet another good reason to eat at least some antioxidant-rich
foods at every meal, according to Agricultural Research Service (ARS)
chemist Ronald L. Prior. To learn more about the effects of
antioxidants on postprandial, or after-meal, oxidative stress, Prior
and co-investigators collaborated in four clinical studies with healthy
The scientists found that the antioxidant capacity of volunteers’
blood plasma samples declined after eating a test meal that lacked
antioxidants. But the scientists also found, for the first time, that
consuming grapes with that same test meal prevented the decline in
plasma antioxidant capacity of the volunteers during the first two
hours following the test meal—the time digestion is the most rapid.
Prior, based at the ARS-funded Arkansas Children’s Nutrition Center
in Little Rock, Ark., noted that omitting antioxidant-rich foods from
meals could lead to cellular damage by free radicals. Such damage is
thought to increase risk of atherosclerosis, cancer and other diseases.
Prior did the work with Liwei Gu and Xianli Wu at the Arkansas
nutrition center; Richard A. Cook at the University of Maine-Orono;
Robert A. Jacob and Gity Sotoudeh, both formerly with the ARS Western
Human Nutrition Research Center, Davis, Calif.; and Adel A. Kader with
the University of California-Davis.
The experiments were part of a larger study that compared the
ability of the human body to use the antioxidants in Bing cherries,
dried plums, dried plum juice, kiwifruit, red grapes, strawberries and
wild blueberries. Scientists used an ARS-developed method called ORAC,
short for Oxygen Radical Absorbance Capacity, to evaluate the fruits’
antioxidant capacity. They documented their findings in 2007 in the
Journal of the American College of Nutrition.
Source : US Department of Agriculture