Anabolic Benefit From the Essential Aminos
Branched chain amino acids (BCAAs) are essential amino acids (must be taken in by the diet) and are among the first supplements used by bodybuilders. The BCAAs are leucine, isoleucine and valine, and their unique branched chain structure enables them to be transported and metabolized by common means. Of the nine essential amino acids, BCAAs are the key players in anabolism and energy metabolism. As well, they account for approximately 20% of our total protein intake and make up about 35% of the essential amino acids in muscle proteins and 40% of the human requirement for preformed amino acids. All in all, current research clearly shows that BCAAs are not only food for muscles, but also important "molecular switches" for turning on anabolism, blunting catabolism, and enhancing recovery.
Of the three BCAAs, research has defined leucine as having the greatest anabolic effect in humans. Studies have shown that it is the rate limiting amino acid for protein synthesis; however, leucine's anabolic effects are dependent on adequate protein and carbohydrate consumption and, as such, those in caloric deficit will not observe leucine's muscle-building properties. Of note, leucine supplementation on its own can deplete stored BCAA's, thus it is best to supplement all three BCAA's together to ensure maximum results under any condition.
BCAAs make up a great proportion of the total amino acid content in skeletal muscle but are also readily broken down (catabolized) during exercise. The status of BCAA breakdown is dependent on the branched-chain a-keto acid dehydrogenase complex (BCKDH) activity, which is relatively dormant under resting conditions and becomes activated with exercise. During exercise stress, BCAAs are reduced to their basic components and are eventually used as fuel for energy. Based on this it is obvious why BCAA supplementation may benefit bodybuilders and athletes undergoing strenuous training.
BCAA supplementation has been used with great success by bodybuilders and strength athletes for many years. But beyond anecdotal reports, the past decade of research has confirmed BCAAs are a "must have" supplement. First, they provide differential anabolic and anti-catabolic effects depending on the training/nutritional status of your muscles. In muscles undergoing regular exercise, BCAAs work as a potent anabolic aid. Molecular level support for BCAAs as anabolic activators comes from recent data illustrating their ability to "turn-on" anabolic signaling pathways via mTOR and p70 S6 kinase in human muscle in the recovery period after exercise. Furthermore, BCAA supplementation has also been shown to reduce muscle soreness and fatigue induced by squatting exercise. On training day subjects ingested either a BCAA cocktail (Leucine:Isoleucine:Valine = 2.3:1:1.2) or a placebo approximately 15 min prior to exercise. The authors reported that those who ingested BCAAs had significantly reduced duration and severity of muscle soreness and fatigue for days after exercise. In contrast, in muscles that are undergoing atrophy (e.g. with corticosteroid treatment, during injury or over training), they can be spared by the anti-catabolic properties of BCAA supplementation.
Recently there has been some interesting research investigating the role of BCAAs in the regulation of central fatigue. It has been shown that exercise increases 5-hydroxytryptamine (5-HT, a.k.a. serotonin) release; thus contributing to exercise-induced fatigue (5-HT affects mood, arousal, and sleepiness). Exercise leads to decreased plasma BCAAs and as exercise progresses there is an elevation in plasma free fatty acids (which promotes an increase in free tryptophan). This causes an imbalance in the free tryptophan to BCAA ratio and promotes increased tryptophan uptake by the brain. 5-HT synthesis is very sensitive to changes in plasma tryptophan levels and the transport of tryptophan across the blood-brain barrier. Ingestion of BCAAs prior to exercise maintains free tryptophan:BCAA homeostasis and, as a result, limits the amount of tryptophan that crosses the blood-brain barrier, thus decreasing 5-HT synthesis and delaying fatigue. The plasma concentration ratio of free tryptophan to BCAAs has been shown to increase by 45% during cycling exercise and by 150% 5 min after exercise. The ratio remains unchanged or even decreased when BCAAs are ingested immediately prior to or during exercise.
Interestingly, research has shown that subjects undergoing strenuous exercise who are given BCAAs report significantly lower ratings of perceived exertion and mental fatigue than those given a placebo. As well, BCAA supplementation can augment brain function through its ability to balance brain tryptophan levels. Those who regularly ingest BCAAs before exercise find that mood and mental function are enhanced. In support, it was shown that subjects who underwent a test of mental attention and flexibility after exercise performed significantly better with BCAA supplementation than with a placebo.
Finally, research has shown that BCAAs support proper immune system function, as they are needed for lymphocytes to synthesize proteins, DNA, and RNA and to undergo cell division. It has been shown in rodents and humans that BCAA restriction results in increased susceptibility to pathogens, leading to a greater number of infections.
Not many other supplements come with decades of evidence substantiating their effectiveness, so you should be convinced that BCAA supplementation is for you. After all, science backs BCAAs to support anabolism and recovery. Furthermore, the added effects of delayed exercise fatigue, increased brain function, and enhanced immunity will keep you working out longer, with greater focus, and better overall health.