Antioxidants are supposed to help us fight disease and aging. They are substances that may protect our cells against the effects of free radicals. Free radicals are molecules produced when the body breaks down food, or by environmental exposures like tobacco smoke and radiation. Free radicals can damage cells, and may play a role in heart disease, cancer and other diseases. Hence the reputation of the antioxidants that neutralize the free radicals.
But pause for a minute. Recent studies at Kansas State University show that they also can cause harm.
Researchers in K-State's Cardiorespiratory Exercise Laboratory have been studying how to improve oxygen delivery to the skeletal muscle during physical activity by using antioxidants. They have found that sometimes antioxidants can impair muscle function.
David C. Poole and Timothy I. Musch, K-State professors from both the departments of kinesiology and anatomy and physiology, and Steven Copp and Daniel Hirai, student researchers in the lab, have conducted various studies associated with how muscles control blood flow and the effects of different doses and types of antioxidants.
Mr. Poole said antioxidants are largely thought to produce better health, but their studies have shown that antioxidants can actually suppress key signaling mechanisms that are necessary for muscle to function effectively.
The studies show that some of the oxidants in our body, such as hydrogen peroxide, are helpful to increase blood flow.
Mr. Poole noted, "We're now learning that if antioxidant therapy takes away hydrogen peroxide - or other naturally occurring vasodilators, which are compounds that help open blood vessels - you impair the body's ability to deliver oxygen to the muscle so that it doesn't work properly....
"If you have a person trying to recover from a heart attack and you put them in cardiac rehab, when they walk on a treadmill they might say it's difficult," Poole said. "Their muscles get sore and stiff. We try to understand why the blood cells aren't flowing properly and why they can't get oxygen to the muscles, as happens in healthy individuals....
"It's really a cautionary note that before we start recommending people get more antioxidants, we need to understand more about how they function in physiological systems and circumstances like exercise."
So the moral is antioxidants are far from being a cure-all. Bumping up intake won't necessarily offer a health boost, largely because the other half of the equation -- pro-oxidants -- are usually ignored in reported research and don't make it into food advertisements. But a balance of both is necessary for normal muscular and blood vessel function.
This isn't the first science-based suggestion that too much of this oft-touted good thing can be harmful. In 2007, a major review of 68 randomized trials on antioxidant supplementation found that treatment with several antioxidants, including beta carotene, vitamin A and vitamin E, was linked to a significant increase in death risk.