Twelve Grams a Day of Leucine Boosts Muscle Mass
People in their seventies who take an extra 4 g leucine with every meal synthesise more muscle mass. Nutritionists at the University of Texas discovered this when they did a small study of eight healthy elderly people.
Leucine is an amino acid that gives muscle cells’ anabolic machinery a boost. Leucine – or one of its metabolites – probably helps muscle cells to ‘see’ that they are being supplied with amino acids and that they need to store these in the form of muscle protein. That’s the rationale behind leucine-based bodybuilding supplements – and some functional foods intended to help patients to retain muscle mass.
But there are also studies which show that leucine doesn’t work. Two disappointing studies were done in the Netherlands. [Am J Clin Nutr. 2009 May; 89(5): 1468-75.] [J Nutr. 2011 Jun; 141(6): 1070-6.] In both of these studies elderly subjects were given 2.5 g leucine at every meal, in one for three months and in the other for six months. In addition the subjects in the studies consumed 1 g protein/kg bodyweight/day.
Nutritionists in Texas will soon publish in Clinical Nutrition the results of a study in which elderly people were also given extra leucine with their meals. But instead of 2.5 g the Texans gave their subjects 4 g leucine at each meal. That meant the subjects got a total of 12 g leucine each day.