A daily intake of 15 g essential amino acids between meals results in an increase of 1.7 kglean body mass in three month's time, researchers at the University of Texas Medical Branch at Galveston discovered. Doesn't sound like much? When we tell you that the subjects in this study were inactive women aged 68, you might change your opinion…
If you don't do weight training you start to lose muscle mass gradually after the age of thirty. At first the process goes slowly and is almost unnoticeable, but the older you get, the faster it proceeds. If you're unlucky you'll lose so much muscle mass that in the end you won't be able to walk or look after yourself. Researchers hope that changing people's diet can help to slow down or stop this process. The Texans are thinking along the same lines.
In 2005 the researchers published the results of a study in which a portion of 6.7 g essential amino acids did help to stimulate the manufacture of muscle protein in people in their early thirties, but not in people in their late sixties. [Am J Clin Nutr. 2005 Nov; 82(5): 1065-73.] From this and other studies the researchers conclude that, for inactive people at least, the optimal anabolic dose of essential amino acids lies somewhere between 6.7 and 15 g per intake.
The Texans were curious to know whether they could stimulate the manufacture of muscle tissue in people in their sixties by using a higher dose of amino acids than 6.7 g, and whether that effect would still be seen after giving their subjects essential amino acids for a period of three months. So they got seven women, average age 68, to take a supplement containing 7.5 g essential amino acids twice a day [SUP]. [The composition is shown below.] That meant that the women took 15 g essential acids in total each day.
The women took the amino acids between meals, and an equal-sized group were given a placebo [PLA].
The body composition of the women in the placebo group hardly changed at all, but that of the women who took the essential amino acids did: their lean body mass increased by 1.7 kg in three month’s time.
The researchers measured the women's protein synthesis just before the start of the experiment and at the end of the three months. They did this once, in the early morning before the women had eaten breakfast [basal], and once after the women had taken a supplement containing 7.5g essential amino acids [EAA].
At the end of the three months the production of muscle tissue continued to rise in the subjects who were still taking the amino acids. In addition, at the end of the three months the subjects' basal muscle growth had increased. The researchers think that this may be because the supplementation boosted the concentration of IGF-1.
"Twice-daily between-meal ingestion of essential amino acid increased lean body mass and the basal synthetic rate of muscle protein in healthy older women", the researchers conclude. "These data provide the rationale for embarking on targeted nutritional interventions in aging and other chronic disease populations undergoing progressive or acute losses in skeletal muscle mass."
J Clin Endocrinol Metab. 2009 May;94(5):1630-7.