This is the finding of research performed by Lydie Combaret, Dominique Dardevet and colleagues at the Human Nutrition Research Centre of Auvergne, INRA, Clermont-Ferrand, France.
After the age of 40, humans start loosing muscle at around 0.5 “2% per year. Immediately after a meal degradation of protein slows down and synthesis doubles. This process is triggered by the arrival of a plentiful supply of amino acids. In older animals this stimulus is less effective; synthesis slows down, and previous work also suggests that breakdown may be affected. While adding leucine to the diet restores protein building there was no knowledge about this supplement's effect on breakdown.
To address this, researchers compared protein breakdown in young (8-month) and old (22-month) rats. They discovered that the slow down in degradation that normally follows a meal does not occur in old animals, so there is excessive breakdown. But adding leucine to the diet restored a balanced metabolism.
The team of researchers believe that the age-related problem results from defective inhibition of ubiquitin-proteasome dependent proteoloysis, a complex degradative machinery that breaks down contractile muscle protein, and that leucine supplementation can fully restore correct function.
"Preventing muscle wasting is a major socio-economic and public health issue, that we may be able to combat with a leucine-rich diet," says senior co-author Didier Attaix.
Commenting on the work Michael Rennie from the University of Nottingham Medical School at Derby says: "This is exciting because it strengthens the idea of a co-ordinated linkage between the meal-related stimulation of protein synthesis and the inhibition of breakdown."
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Belinda Linden, head of medical information at the British Heart Foundation says the study suggests that light to moderate alcohol consumption may only give a small amount of protection against coronary heart disease, while the benefits of moderate to heavy drinking are likely to be outweighed by the overall harm that alcohol can cause.
She also says there does not appear to be any evidence to suggest that light to moderate alcohol consumption will actually harm the heart, however over indulging can have an adverse effect on your health.
Linden says people should not be encouraged to start drinking specifically to protect their heart, as there are much safer options and their advice remains that the best way to reduce the risk of heart disease is to quit smoking if you smoke, increase levels of physical activity and eat a healthy balanced diet.
The study is published in The Lancet.