New York: The amino-acid leucine, found in protein, may help to prevent age-related muscle loss.

French researchers, who tested elderly rats, found that a leucine-supplemented diet restored a more youthful pattern of muscle-protein breakdown and synthesis when added to the diet. The older animals had shown a tendency toward excessive protein breakdown before going on the leucine-rich diet, but the amino acid appeared to erase that imbalance, according to findings published in the December issue of the Journal of Physiology.

Leucine is an essential amino acid, which means the body cannot manufacture it and it must be ingested through dietary protein. Along with other essential amino acids, leucine helps maintain muscle mass — which has made leucine-containing supplements a favorite of bodybuilders and athletes.

It’s well known that after the age of 40 or so, people gradually lose muscle mass, and it’s thought that an imbalance in muscle-protein synthesis and breakdown is involved.

In younger people, this process is typically in balance. For example, research shows that after a meal, muscle-protein breakdown slows, whereas synthesis ramps up in response to the influx of amino acids from food.

But in the new study, older rats did not show this post-meal dip in protein breakdown, whereas their younger counterparts did. A short time on the leucine-supplemented diet, however, restored a youthful pattern of protein breakdown in the elder rats.

The researchers are currently studying whether the same might be true of older adults, study co-author Didier Attaix, of the Institut National de la Recherche Agronomique in Ceyrat, told Reuters Health.

Leucine is one of the building blocks of protein, particularly from animal foods, and it can be consumed through meat, dairy, soy, beans and other protein-rich sources. It’s also widely sold as a dietary supplement.

There is research evidence, Attaix noted, that leucine supplementation can help build muscle in humans, though he said he is not aware of any studies that have focused on elderly adults.

Preventing age-related muscle loss is important, Attaix and his colleagues point out, because muscle wasting contributes to physical disability and poor overall health in the elderly.

Attaix said they suspect that as people age, the metabolic system that inhibits muscle-protein breakdown after a meal starts to become insensitive to the normal effects of food. It’s possible, he speculated, that high leucine concentrations in the body can counter this — though that remains to be demonstrated in future studies.