December 11, 2005
Leucine Stops Muscle Breakdown In Aging Rats

Don't want to become less muscular as you age? Here is news you can probably use.

Muscle in adults is constantly being built and broken down. As young adults we keep the two processes in balance, but when we age breakdown starts to win. However, adding the amino acid leucine to the diet of old individuals can set things straight again. 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 0.52% 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."

Here for the convenience of American readers is a Froogle Google search on Leucine.

No, I do not know what would be an appropriate human daily dose. Does any reader have an informed basis for estimating a reasonable daily leucine dose?

Share |      Randall Parker, 2005 December 11 09:12 AM  Aging Diet Studies

back40 said at December 11, 2005 2:35 PM:

I think you just need a good diet. Maybe old people who have less appetitie could use supplements.

Marvin said at December 11, 2005 3:48 PM:

Leucine, Isoleucine, and Valine are all branched chain amino acids(bcaa's). They've been used by body builders and weightlifters for many years to build muscle. Whey protein is quite high in the bcaa's . I would recommend 20 grams of whey protein for anyone over the age of 40 or so, taken within an hour of strenuous or prolonged exercise. As a routine maintenance daily dose for people over 60, a gram of leucine or so daily would be plenty. Animal proteins are fairly high in bcaa's, so meat eaters should get plenty--but they need to watch the saturated fats.

Putting seniors on daily HGH is an even better way of maintaining lean muscle mass.

PacRim Jim said at December 12, 2005 10:19 AM:

Nerds, beware!

Lou Pagnucco said at December 12, 2005 2:32 PM:

Muscle loss during aging is also associated with lack of excercise, acidosis and low grade systemic inflammation.

Hopefully correcting these will also prevent muscular atrophy and frailty.

Josh Mitteldorf said at December 13, 2005 5:22 AM:

Here's an original article from J Nutrition 132:95-100 (2002)

Postprandial stimulation of muscle protein synthesis in old rats can be restored by a leucine-supplemented meal.

In this study, they used 50g leucine per Kg of feed, corresponding to .012 g per Kcalorie. For a human who eats 2000 Kcal per day, this would correspond to 24 g of leucine, which is a lot of pills to take. The point is that protein is a macronutrient, and we're used to supplementing micronutrients.

A further caution: leucine is associated with stimulating the body's insulin response, which has a general pro-aging effect.

Kevin said at December 13, 2005 10:23 AM:

If you want to see muscular rodents, google "myostatin mouse" or check out

Now that's muscle!

Rob said at December 14, 2005 12:12 PM:

Oh man, are my old mice going to be glad to hear about this!

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