Effect of amino-acid intake on physical conditions and skin state: a randomized, double-blind, placebo-controlled, crossover trial

The objective of this study is to elucidate the effect of a supplement enriched with L-leucine, L-arginine, and L-glutamine on body compositions/skin conditions. Healthy young women (n = 29) were allocated to a group (n = 14) receiving an amino-acid supplement (600 mg L-leucine, 250 mg L-arginine, and 300 mg L-glutamine) and a placebo group (n = 15) receiving a supplement not-containing the amino acids. The amino-acid supplement and placebo were given twice/day for 6 weeks. After a wash-out (2 months) from the 1st test, the amino-acid group received the placebo and the placebo group the amino-acid supplement. The body compositions/ skin conditions were measured 4 times (day 1 and weeks 2, 4, and 6) in each test. Percentage-change of muscle mass in the amino-acid group increased up to 4 weeks (p = 0.05) and was higher than that in the placebo group (p = 0.09). Skin texture estimated by the image processing of neck skin replica tended to increase in the amino-acid group at 6 weeks compared with that at 0 week, though there was no significant intergroup difference. In conclusion, the young adult women having no fitness habit showed the significant increase of the muscle amount and improvement tendency of the skin texture by the continuous intake of the amino-acid supplement.