If you’ve been following along then by now you’ve figured out that science has proven that even less than half a gram of protein per pound of bodyweight per day is enough to both retain and build muscle mass. Today I’d like to look into amino acids to see what we can learn and also to see if I can wrap this series up.
Obviously, the important component of the protein seems to be the essential amino acid content. It is now clear that muscle anabolism occurs with ingestion of only the essential amino acids meaning the non-essential amino acids are unnecessary to stimulate muscle growth following exercise(1). However, this doesn’t mean that essential amino acid supplements are superior to non-essential or to whole proteins. It simply means that essential amino acids can stimulate muscle protein synthesis and there are ample non-essentials to support the elevated levels of synthesis.
Leucine may be the most important amino acid for stimulation of muscle protein synthesis. Leucine, along with isoleucine and valine, is a branched-chain amino acid (BCAA). BCAAs are often touted as the most anabolic amino acids and many BCAA supplements are sold and bought up hungrily by bodybuilders and athletes alike.
In animal studies leucine stimulates pathways inside the muscle cells that result in increased muscle protein synthesis in rats following intense exercise that would otherwise decrease synthesis(2,3). This means that in a catabolic exercise model, leucine ingestion may be very effective as an anabolic agent. The evidence in humans is less clear, particularly following resistance exercise.
Similar results were found in a recent study from a research group in Galveston, Texas. There is evidence that leucine may decrease the amount of muscle protein breakdown in humans, but these studies did not involve exercise(4). The Galveston results demonstrated that the NBAL was not improved with additional leucine, further casting doubt on the efficacy of leucine supplementation following anabolic exercise in humans. It should be noted, however, that few studies have actually examined this issue and an in-depth evaluation may be required before leucine can be dismissed as an anabolic agent.
When we next get together, or more correctly when I next find the time seeing as I didn’t wrap this up because there is still one more thing to cover, I’ll finish this series off by looking at protein timing and seeing if there are any advantages to be found there in order for us to find a way to convince our muscles to grow with proper nutrient intake at the correct times. Until then my friends,
1. Am J Physiol 1999; 276(4 Pt 1):E628-E634
2. Chittenden RH: The Nutrition of Man. London, Heinemann, 1907
3. J Sports Med Phys Fitness 2002; 42(3):340-347
4. Am J Clin Nutr 2007; 85(4):1031-1040
This article was written and researched by Matt Taylor
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