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Branched-chain amino acids, or BCAA’s, have become popular enough in weight rooms or on supplemental shelves to rival other top supps like whey. Manufactures claim BCAAs are a must to anyone trying to get swole or maintain muscle mass while losing weight. Increasingly, climbers looking for an edge can be seen sipping the neon green or pink slurries in gyms and at crags.
But do they work?
Brace yourself, the science is messy. First up, an overview of muscle protein synthesis: 20 amino acids comprise muscle protein. The body cannot produce nine of the 20 in physiologically significant amounts, thus those nine are known as essential amino acids (EAAs). All of the EAAs, along with the 11 non-essential amino acids, are required in adequate amounts to build muscle. BCAAs are three of the nine EAAs: leucine, isoleucine, and valine. These three are widely considered most important for building muscle.
Muscle protein turnover happens all the time. Turnover, or the breaking down and re-building of muscle, is important for renewing muscle fibers, which increases muscle contraction efficiency and therefore increases strength. If more muscle is being broken down than is being synthesized, the body is considered to be in a catabolic state. If more is being synthesized than broken down, the body is considered to be in an anabolic state.
When in a fasted state (8-12 hours after your last meal), all EAAs for muscle protein synthesis come from muscle protein breakdown. Studies consistently find that at this point, muscle breakdown will exceed muscle synthesis, owing to the fact that there is a net flux of EAAs from breakdown into plasma and oxidative pathways. More specifically, it has been reported that muscle breakdown exceeds synthesis by 30% in the fasted state.
Most commonly, BCAA users will consume BCAAs as a pre-workout. Manufacturers will mix BCAAs with caffeine and electrolytes to round off the pre-workout powders, or they will leave the BCAAs “raw” for clean eaters. Oftentimes, people that do intermittent fasting (an adjusted eating schedule with a “fasting” time and “re-feed” window) will take BCAA’s while in the fasted state and while training.
A recent review paper of other studies, written by Robert R. Wolfe and published by the Journal of the International Society of Sports Nutrition, highlighted why BCAA users should not consume BCAAs in a fasted state.
Because all EAAs are required for building muscle, then consumption of BCAAs can only increase muscle synthesis if the efficiency of recycling and reincorporating the other six EAAs is also increased. But, if no other protein source is consumed with BCAAs, then protein breakdown is the only source of replenishing those other EAAs. Inducing an anabolic (building) state following the consumption of BCAAs while in the fasting state would therefore be theoretically impossible. Even with the most generous predictions about the intricate muscle protein pathways, the highest increase in protein synthesis that could be seen would be from 0.050% to 0.057%, which would be difficult to accurately measure, according to Wolfe.
The few studies that do measure protein synthesis following BCAA consumption back Wolfe’s theories. A study led by Louard et al. found that BCAA infusion increased plasma concentrations of BCAAs four-fold. Instead of observing increased muscle protein synthesis, muscle protein synthesis significantly decreased. The same results were obtained by another study led by the same investigators when the BCAA infusion was extended to a longer timer period. BCAA plasma concentrations increased from five to eight fold, but muscle protein synthesis was still significantly decreased. Additionally, total muscle protein turnover was decreased.
Both studies concluded that the catabolic state was not reversed following BCAA infusion and that the reduction of muscle protein turnover would have a “detrimental effect on muscle strength.”
But, fear not if you have BCAAs on your supp shelf at home. A study published in the American Journal of Clinical Nutrition found that 5 grams of BCAAs plus 6.25 grams of whey protein (11.25 grams total) had the combined effect that would be induced by 25 grams of whey protein. So while on their own they are not effective, BCAAs plus a complete protein source may augment the muscle-building impact of the protein.
One more thought worth mentioning: One of the reasons many BCAA consumers have traditionally consumed it first thing in the morning in the post-absorptive state is that BCAAs reduce serotonin levels. Low serotonin levels have been linked to depression and irregular appetite, sleep and mood. Many BCAA users suggest taking the supp in the morning to counteract those effects because after you work out, you eat a carb-heavy meal, which will help the body return to normal hormonal levels throughout the day. Taking BCAA’s too late, on the other hand, would disrupt sleep/eating cycles and potentially compound the low-serotonin effects.
Ultimately, climbers should learn to do their research before purchasing and using BCAAs. You could be encouraging your body to breakdown more muscle simply by taking this supp at the wrong time and on an empty stomach. Your best bet is to consume BCAAs with a complete protein source in the morning and before working out.