are anabolic hormones, such as testosterone
, growth hormone
and insulin
. It turns out that BCAA
s stimulate the activity of all three anabolic hormones, which may help explain why BCAAs spare muscle protein.5 Leucine
in particular potently partners with insulin, which is anticatabolic and which, along with the essential aminos
, encourages muscle protein synthesis. Several studies point to leucine
as a means of maintaining muscle, while dieting to lose body fat. If you do aerobics while dieting, taking a BCAA supplement prior to training-a dose of about five grams ought to do it - will prevent muscle loss. To get the most out of the BCAAs, include a source of vitamin B1
, or thiamine, which is required for BCAA metabolism. A B-complex vitamin 
would work. - Shimomura, Y., et al. (2004). Exercise promotes BCAA catabolism: Effects of BCAA supplementation on skeletal muscle during exercise. J Nutr. 134:1583S-1587S.
- Tang, F. (2006). Influence of branched-chain amino acid supplementation on urinary protein metabolite concentrations after swimming. J Am Coll Nutr. 25:188-94.
- Busquets, S., et al. (2000). Branched-chain amino acids inhibit proteolysis in rat skeletal muscle: Mechanisms involved. J Cell Physiol. 184:380-84.
- Shimomura, Y., et al. (2006). Nutraceutical effects of branched-chain amino acids on skeletal muscle. J Nutr. 136:529S-532S.
- De Palo, E., et al. (2001). Plasma lactate, GH and GH-binding protein levels in exercise following BCAA supplementation in athletes. Amino Acids. 20:1-11.
- Blomstrand, E. (2001). Amino acids and fatigue. Amino Acids. 20:25-34.
- Rieu, I., et al. (2006). Leucine supplementation improves muscle protein synthesis in elderly men independently of hyperaminoacidemia. J Physiol. 575:305-315.
