27 January 2010

Antioxidants found to impair muscle function

by Kate Melville

Antioxidants increasingly have been praised for their benefits against disease and aging, but new studies at Kansas State University show they can also seriously impair muscle function by limiting oxygen in the bloodstream.

The discovery, reported in the Journal of Applied Physiology, came about while the researchers were studying how to improve oxygen delivery to the skeletal muscle by using antioxidants. Instead, they found that sometimes antioxidants can impair muscle function.

"Antioxidant is one of those buzz words right now," said K-State's Steven Copp, a doctoral student in anatomy and physiology. "I think what a lot of people don't realize is that the antioxidant and pro-oxidant balance is really delicate. One of the things we've seen in our research is that you can't just give a larger dose of antioxidants and presume that there will be some sort of beneficial effect. In fact, you can actually make a problem worse."

The researchers conducted various studies associated with how muscles control blood flow and the effects of different doses and types of antioxidants. Copp explained that abnormalities in the circulatory system, such as those that result from aging or a disease like chronic heart failure, can impair oxygen delivery to the skeletal muscle and increase fatigue during physical activity.

The researchers do acknowledge that there is a potential for antioxidants to reverse or partially reverse some of those changes that result from aging or disease. But the new studies have shown that some of the oxidants in our body, such as hydrogen peroxide, are helpful to increase blood flow.

"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," co-researcher David Poole explained.

Poole said the research has shown that antioxidants can actually suppress key signaling mechanisms that are necessary for muscle to function effectively. "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," he concluded.

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Source: Kansas State University