Recent research suggests that supplementing with branched-chain amino acids (BCAAs) before, during and after a workout can help maintain and build muscle. So what’s that mean on a practical level for someone looking to get leaner and stronger? It might mean that it supplementation is a good idea, and BCAAs are relatively cheap and probably harmless. But the research is not completely clear. For most people, it’s probably more important to just focus on proper protein intake and forget about amino acids.
What are BCAAs?
Amino acids are the building blocks of protein and proteins, among other things, are the building blocks of muscles (and much else in our bodies). Of the common amino acids, eight (some nutritionists would say nine) are considered “essential”. In fact all the common amino acids are essential, but our body is good at synthesizing some, but not others. The ones we can’t readily synthesized must be obtained from our food and are therefore considered to be essential dietary components.
Three of these essential amino acids (leucine, isoleucine and valine), are called branched-chain amino acids because their chemical structure includes a branch off the main molecule. These three amino acids make up roughly one-third of human muscle. They also perform essential functions during exercise, such as regulating blood sugar levels, aiding in healing and the production of growth hormone. It may seem surprising, but when we exercise hard, our body breaks down muscle to free up the BCAAs it needs to help with these basic functions.
Why take BCAA Supplements?
In theory, BCAA supplementation could have two beneficial effects:
- making BCAAs available during exercise so that muscle need not be destroyed to release BCAAs into the blood, thus preventing muscle breakdown
- making BCAAs available during the healing process, making this essential component of muscle available to help in muscle repair and growth.
Numerous studies over the years have in fact found that BCAA supplementation significantly decreases muscle breakdown in both endurance and strength athletes. In the most recent available study (April, 2010), Sharp and Pearson  tested the effects of BCAA supplementation on levels of cortisol, creatine kinease and testosterone in the blood. Cortisol is a “catabolic” hormone and a marker of muscle breakdown. Testosterone is, of course, the most well-known “anabolic” hormone and a marker of muscle growth. Creatine kinease is also a marker of muscle breakdown. Sharp and Pearson found, with a high degree of confidence, that in fact BCAA supplementation before, during and after exercise significantly lowered the levels of cortisol and creatine kinease and significantly increased the levels of testosterone. In other words, it prevented muscle breakdown and promoted muscle growth. Furthermore, the effects were detectable for days after exercise.
There are two things to note in this study:
- It concerned “overreaching”, that is to say short term increases in training volume. In their testing, they had athletes perform 8 exercises for three sets, where the subjects failed at 6–8 repetitions. That is to say, relatively high weight.
- They exempted from their study anyone getting more than the recommended allowance of protein (0.8gms/kg of lean body mass for a sedentary person). Previous studies have shown that in fact endurance athletes require more like 1.2–1.4 gms/kg and strength athletes trying to build muscle should take in 1.4–1.8gms/kg . I think this is a serious limitation in this study and would like to see how it compares to people who are watching their protein intake and getting amounts more in line with recommendations for athletes during bouts of intense training.
How Much Should I Take?
Taking too many BCAAs can case a variety of problems. At the extreme end, too much leucine can cause the skin disease pellegra and too much valine can even cause hallucinations, though these have to be taken in very high quantities. In animal testing, no animals died with doses of 10gm/kg body weight and no toxic effects were observed with doses of 2.5 gm/kg/day for 3 months or 1.25 gms/kg/day for one year. These are large doses compared to typical sports supplementation and as of 2004 there were no reports of toxicity related to sports supplementation. Nevertheless, it is worth being away of the fact that truly excessive doses could have negative side effects. One key recommendation is not to supplement with leucine alone, but to take the amino acids in the same proportions they are typically found in animal proteins, which Shimomura et al give as two parts leucine to one part each of isoleucine and valine .
So how much is enough? One study found that supplementation with 77mg/kg of body weight (roughly 5.6 grams for a 160 pound individual) significantly decreased muscle breakdown. Note that this dose is one sixteenth the dose tested as safe when taken daily for a year. Other studies, used amounts varying from 12gms/day to 40gms/day. However, Sharp and Pearson administered only 2.8gms/day (0.7gms valine and isoleucine, 1.4gms leucine) and yet found significant reduction in cortisol and creatine kinease levels and significant increases in testosterone levels. So from that it seems like a very safe dose of 3gms per day in the 2:1:1 ratio suggested above will have significant beneficial effects on athletes during a bout of high-intensity training.
Other studies (cited in ) have shown that even with relatively high levels of protein intake, levels of BCAAs decreased during extended periods of intense training and that BCAA supplementation on the order of 60mg of leucine per kg of body mass helped prevent muscle breakdown. This would be roughly 4 gms of leucine for a 160-pound individual, which would require 8gms/day amino acid supplementation. Note this is still one tenth the dose tested as safe, but prudence would suggest cycling through amino acid supplementation only during times of intense exercise when muscle breakdown would be greatest.
So in short, as little as 3gms per day should have significant beneficial effects, but the maximum effect may be achieved on higher doses. Athletes should be careful not to go crazy with it though as at a certain level, BCAA supplementation could cause health problems. That said, it seems that additional studies are needed to clarify whether BCAAs in isolation have some significant advantage over a basic diet with adequate protein intake. Without such studies, it seems like good intake of protein and carbohydrates would be more beneficial. If you exercise while you’re calorie depleted, a few BCAAs are not going to stop muscle breakdown. You’re body is going to need to fuel itself so any missing nutrient, carbs, protein or BCAAs will force it to break down muscle.
Each gram of whey protein, for example, has 103mg of leucine. So your typical 30gm scoop of whey protein powder has 3gms of leucine. That doesn’t count any dietary leucine you’re getting from regular food. This means that the typical athlete getting adequate protein is already getting adequate leucine. Is there some magic effect from taking BCAAs alone immediately before exercise, compared to whey protein? If you know of a study that compares those two cases, I’d love to hear about it. So for the time being, I got for a the cheapest, unsweetened and unflavored (important!), high-quality whey protein isolate that I can find. For the past several years, that has been the Now Nutrition Whey Protein Mega Pack — same stuff as the others at a much lower price.
Carwyn P.M. Sharp and David R. Pearson, “Amino acid supplements and recovery from high-intensity resistance training,” Journal of Strength and Conditioning Research 24/4 (April, 2010), pp. 1125–1130.
Josephine Conolly-Schoonen, “Dietary Protein Intake Differences Based on Activity Levels,” Medscape, 03/06/2001 (free subscription required for access).
Yoshiharu Shimomura, Taro Murakami, Naoya Nakai, Masaru Nagasaki and Robert A. Harris, “Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise,” Journal of Nutrition 134:1583S-1587S, June 2004 (Supplement: 3rd Amino Acid Workshop).
 MacLean, D. A., Graham, T. E. & Saltin, B. (1994) “Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise,” Am. J. Physiol. 267: E1010–E1022 (cited in Shimomura et al, no. 1 above).