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Thursday, December 2, 2010

Better to Eat Protein Before Exercise, or After?

From Reuters Health Information

NEW YORK (Reuters Health) Nov 30 - Eating protein after exercising may help rev up the body's muscle-making machinery, in both young and older men alike, a small study suggests.

In 48 men - half in their twenties and the other half in their seventies -- consuming a protein drink after exercise led to a greater increase in muscle protein synthesis, compared with downing the drink after a period of rest.

What's more, muscle protein increased at nearly the same rate in young and elderly men, the researchers reported online November 17th in the American Journal of Clinical Nutrition.

That suggests that, contrary to some researchers' speculation, older age may not impair the way the body digests and absorbs protein from food, according to the researchers, led by Dr. Luc JC van Loon of Maastricht University Medical Center in the Netherlands.

The study has a number of limitations. Besides its small size, it did not look at actual muscle mass changes over time -- but only short-term changes in participants' muscle-fiber proteins after the protein drink. So it is not clear what kinds of gains older or younger adults might see from having their protein post-workout.

Still, the authors do suggest that exercising before consuming protein may lead to improved muscle protein synthesis.

And for older adults, they write, exercise should "clearly" be considered as a way to boost muscle-protein buildup in response to food -- and, by extension, to support healthy aging.

The study included 24 older men with an average age of 74 and 24 young men with an average age of 21, none of whom regularly exercised.

The researchers randomly assigned the men to one of two groups; in one, the men rested for 90 minutes, followed by 30 minutes of exercise -- pedaling a stationary bike and performing light strengthening exercises. In the other group, the men spent those additional 30 minutes relaxing.

Afterward, men in both groups drank a solution containing 20 grams of protein, then had their blood levels of various amino acids repeatedly measured. The researchers also took a small sample of tissue from each man's thigh muscle, right before the protein drink and 6 hours afterward, to measure protein changes in the muscle.

Overall, muscle protein increased to a greater extent in the exercise group versus the inactive group, and both older and younger men showed similar benefits.

It's well known that muscle mass tends to wane as people age, and some researchers have proposed that one reason may be that in older people, the body's muscle-protein production responds less efficiently to protein from food, and also to exercise.

However, the current findings suggest that this may not be the case.

"Effective dietary approaches are needed to prevent and/or attenuate the age-related loss of muscle mass," Dr. van Loon and his colleagues write.

Based on these findings, they conclude, it's possible that having protein after exercise allows for greater use of food-derived protein for muscle building, in young and old alike.

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