Antioxidants aren't always good for you and can impair muscle function, study sh

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http://www.eurekalert.org/pub_releases/2010-01/ksu-aaa012610.php

Antioxidants aren't always good for you and can impair muscle function, study

shows

Antioxidants increasingly have been praised for their benefits against disease

and aging, but 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, which are nutrients in foods that can prevent or

slow the oxidative damage to the body. Their findings show that sometimes

antioxidants can impair muscle function.

" Antioxidant is one of those buzz words right now, " said Copp, a doctoral

student in anatomy and physiology from Manhattan and a researcher in the lab.

" Walking around grocery stores you see things advertised that are loaded with

antioxidants. 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. "

C. Poole and I. Musch, K-State professors from both the

departments of kinesiology and anatomy and physiology, direct the

Cardiorespiratory Exercise Laboratory, located in the College of Veterinary

Medicine complex. Researchers in the lab study the physiology of physical

activity in health and disease through animal models. Copp and Hirai, an

anatomy and physiology doctoral student from Manhattan working in the lab, have

conducted various studies associated with how muscles control blood flow and the

effects of different doses and types of antioxidants.

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 fatigability during physical activity, Copp said. The

researchers are studying the effects antioxidants could have in the process.

" 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. "

Copp said there is a potential for antioxidants to reverse or partially reverse

some of those changes that result from aging or disease. However, K-State's

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, " Poole said.

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.

" 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, " Poole said.

Hirai said the researchers will continue to explore antioxidants and the effects

of exercise training. Their studies are looking at how these can help

individuals combat the decreased mobility and muscle function that comes with

advancing age and diseases like heart failure.

" The research we do here is very mechanistic in nature, and down the road our

aim is to take our findings and make recommendations for diseased and aging

populations, " Copp said.

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The researchers have published their recent findings in several journals,

including the Journal of Applied Physiology, Respiratory Physiology and

Neurobiology, Microvascular Research, The American Journal of Physiology and

Experimental Physiology.

The Cardiorespiratory Exercise Laboratory has been funded by grants from the

National Institutes of Health, American Heart Association and intramural awards

from the College of Veterinary Medicine.