ScienceDaily (Jun. 28, 2007) — They’ve been said to stall aging, ward off disease and wage internal war against the harmful free radicals that pummel our bodies every day. But just how well do antioxidants—those all-powerful compounds often found in richly colored fruits and vegetables, such as blueberries, blackberries and red cabbage—actually perform inside the human body?

Nutritionists with the Agricultural Research Service (ARS), the U.S. Department of Agriculture’s chief scientific research agency, recently tackled this question. Their findings appear in the current issue of the Journal of the American College of Nutrition.

Led by Ronald Prior, an ARS chemist who works at the Arkansas Children’s Nutrition Center in Little Rock, the researchers investigated how the consumption of different fruits affected volunteers’ antioxidant status.

They did this by measuring the plasma (blood) antioxidant capacity (AOC) of volunteers who’d just ingested blueberries, cherries, dried plums, dried-plum juice, grapes, kiwis or strawberries.

The series of ARS studies confirmed what many antioxidant experts have long suspected: that the free-radical-busting compounds found in foods are quite complex, with some apparently being easier to absorb and utilize than others.

For instance, the researchers found that despite their high antioxidant content, plums did not raise plasma AOC levels in volunteers. According to Prior, one of the major phytochemicals in plums is chlorogenic acid, a compound not readily absorbed by humans.

As for the wild blueberry, a larger-than-average serving of this much-heralded antioxidant source was needed to boost plasma AOC levels. A noticeable climb in AOC wasn’t detected until volunteers consumed at least a half-cup serving of the berries.

The volunteers’ consumption of grapes and kiwifruit both led to noticeable spikes in plasma AOC. But it’s not clear yet which compounds were responsible for the increased levels.

Alternatively, when volunteers were asked to consume a shake containing protein, carbohydrates and fat, with no antioxidants, their blood antioxidant levels dropped.

While additional research is needed to determine if elevated plasma AOC levels translate to a lower risk for chronic degenerative disease, the current ARS study is an important first step in efforts to establish recommendations for antioxidants in the diet.

USDA/Agricultural Research Service (2007, June 28). Not All Antioxidants Are Created Equal. ScienceDaily. Retrieved December 4, 2007, from http://www.sciencedaily.com

Will Dunham, “Study shows vitamin C’s cancer-fighting properties”, Reuters India, September 11, 2007,
Link: http://in.reuters.com/article/worldNews/idINIndia-29449820070910

Vitamin C can impede the growth of some types of tumors although not in the way some scientists had suspected, researchers reported on Monday.

The new research, published in the journal Cancer Cell, supported the general notion that vitamin C and other so-called antioxidants can slow tumor growth, but pointed to a mechanism different from the one many experts had suspected.

The researchers generated encouraging results when giving vitamin C to mice that had been implanted with human cancer cells — either the blood cancer lymphoma or prostate cancer. Another antioxidant, N-acetylcysteine, also limited tumor growth in the mice, the researchers said.

Antioxidants are nutrients that prevent some of the damage from unstable molecules known as free radicals, created when the body turns food into energy. Vitamin C, vitamin E and beta-carotene are among well-known antioxidants.

Previous research had suggested that vitamin C may stifle tumor growth by preventing DNA damage from free radicals.

But researchers led by Dr. Chi Dang, a professor of medicine and oncology at Johns Hopkins University in Baltimore, found that antioxidants appear to be working in a different way — undermining a tumor’s ability to grow under certain conditions.

Figuring out how antioxidants impede tumors should help scientists figure out how they might be harnessed to fight cancer, Dang said. In addition to the cancer types involved in this study, others that might be vulnerable to vitamin C include colon cancer and cervical cancer, he said.

Dang said more research is needed and cautioned against taking high doses of vitamin C based on these findings.

“Certainly we would very much discourage people with untreated cancer to go out and take buckets full of vitamin C,” Dang said in a telephone interview.

Linus Pauling argued in the 1970s that vitamin C, also called ascorbic acid, could ward off cancer, but the notion has proved contentious.

Pauling, who won the Nobel Prize in chemistry as well as the Nobel Peace Prize, died in 1994.

“Pauling actually had some good evidence that under certain situations vitamin C can prevent tumor formation. It’s just the mechanism was really not that clear then,” Dang said.

“Now that, I think, we provide relatively compelling evidence of how this works, maybe Pauling is partly