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05.11.2008

Anti-oxidants stimulate muscle protein synthesis in elderly

Just like old people, elderly rats lose muscle mass because their bodies make less muscle protein. Researchers at INRA in France have discovered that anti-oxidants may be a way to do something about this. Elderly rats that get extra rutin [structural formula below], vitamin E, vitamin A, zinc and selenium in their food manufacture the same amount of muscle protein as young rats, according to INRA.

Study
The researchers wanted to know whether elderly people's bodies deal less efficiently with proteins and amino acids because an older body also experiences more oxidative stress and inflammatory reactions. If this is the case, then it should be possible to do something about it with simple anti-oxidants that are also found in food. So the researchers added an anti-oxidant cocktail to the diet of eight-month-old and twenty-month-old rats. The rats were given the supplements for a period of seven weeks.

The only ingredient in the anti-oxidant mix that you might not be familiar with is rutin. Rutin is a glycoside analogue of the flavonoid quercetin, which is found in buckwheat, citrus fruits, noni, black tea and apple peel. It's not a particularly special substance: it could well be the most common flavonol in fruit and vegetables.

Studies have shown that rutin has "antibacterial, antiviral, antioxidant, antiproliferative, antiinflammatory, and anticarcinogenic effects", the researchers write.

Vitamin E and vitamin A are anti-oxidants, and the body uses zinc and selenium as co-factors to produce endogenous anti-oxidants, such as the enzymes superoxide-dismutase and glutathione peroxidase. At the end of the seven weeks the researchers determined how much muscle protein had been manufactured in a muscle in the forepaw of the rats, by mixing the muscle tissue with the amino acid phenylalanine in a test tube.

The researchers then recorded how quickly the muscles absorbed the amino acid. They assumed that the muscles absorb the amino acid so that they can use it to make protein. The researchers then gave the muscle tissue another amino acid, leucine, so that it would start to grow.

Results
AAox- = young adult rats without supplement; AAox+ = young adult rats with supplement; OAox- = old rats without supplement; OAox+ = old rats with supplement.

The supplement had no effect on the young animals, but did have an effect on the old rats. The muscles of the old rats absorb as much phenylalanine as the muscles of the young adults.

Leucine delays the breakdown of protein in muscles. In the old rats the anti-oxidant mix enhances this effect.

The muscles of the old rats that had been given the anti-oxidant mix were mostly larger and heavier, but the effect was not statistically significant. "It may be postulated that a longer period of supplementation would be necessary to have a significant effect on muscle mass", the researchers speculate.

Conclusion
If other studies confirm INRA's findings, then older weight trainers may be able to get more out of their protein-rich diet by increasing their intake of anti-oxidants. Supplements manufacturers could enrich their protein powders and bars with extra vitamin C, more vitamin E, forest fruits extract, resveratrol...

The researchers advise caution, however. Before you start adding extra anti-oxidants it's important to know for sure that they are safe. And an anti-oxidant like vitamin A, or its precursor beta-carotene, should certainly not be used in high concentrations.

Sources:
J Nutr. 2008 Nov;138(11):2205-11.