What are BCAAs?BCAAs are three of the eight essential amino acids (EAAs), comprising valine, leucine, and isoleucine. These three BCAAs are so called because they have a branched molecular configuration (which brings back happy nerdy memories of drawing amino-acid diagrams during my nutrition degree!). BCAAs are hugely important for health because they make up one-third of muscle protein, can be used directly as fuel by the muscles, and can be converted into glutamine and alanine — two other important amino acids that are released in large quantities during aerobic exercise. Unsurprisingly, then, BCAA supplements are consistently popular with people who lead an active, healthy lifestyle. But what are BCAA supplements and how do you choose a good one, if you choose one at all? See also: My half marathon training regimen: proven supplements for runners
Why do people supplement with BCAAs?The rationale behind supplementing with BCAAs is that these three amino acids promote muscle synthesis (anabolism) and help prevent muscle breakdown (catabolism). As such, they are prized by both endurance athletes looking to maintain lean muscle mass and bodybuilders and others looking to gain bulk and prevent muscle soreness and injury.
Leucine, isoleucine and valineLeucine, isoleucine, and valine are naturally occurring amino acids found in protein rich foods. They are also normally present in high amounts in whey protein and some other protein supplements. Because BCAAs are so ubiquitous in muscle, the richest sources of BCAAs are animal foods. Anyone eating a plant-based diet may find BCAA supplements helpful for making up shortfalls in these essential amino acids, although care should be taken to also ensure a good overall intake of plant protein — from legumes, pulses, nuts, and seeds, for instance — to get all the amino acids required for health. BCAAs are considered generally safe for use at the amount recommended (check product labels) but could reduce the absorption of other essential amino acids if taken in excess. In addition, and as we’ll get to later in the post, the cellular growth pathways initiated by BCAAs not only cause muscles to grow, they may also cause the growth of cancer cells as well, so exercise caution with these supplements. 1 Also, anyone with a kidney issue should consult a health care practitioner before taking BCAAs. In some cases, supplementing with BCAAs may be a part of kidney disease management. 2
Possible BCAA supplement benefitsIn a word, muscle growth. Leucine in particular has been shown time and again to play a unique role in stimulating muscle protein synthesis (MPS),3 with more recent studies finding an additive effect when all three BCAAs are taken together.4 Essential amino acids (EAAs) in general have been found to stimulate mechanistic target of rapamycin complex-1 (mTORC1) signaling. mTORC1 is a protein complex that activates translation of proteins in order for cells to grow and proliferate.
Dosing BCAAs for athletic performanceIf you’re going to use for athletic performance, in practical terms, studies show that taking around 4-6 grams of BCAAs during and after exercise can help increase MPS by around 22%. 5 However, greater increases in MPS have been seen with whey protein supplements taken after exercise that contain all essential amino acids including BCAAs. 6
Recovery for endurance athletesBCAA supplementation may, however, offer particular benefits for improving MPS at rest, such as when a person is on bed rest or recovering from injury. 5 7 And, BCAAs seem to be helpful in reducing muscle breakdown, damage, and soreness in endurance athletes, 8 and delayed onset muscle soreness (DOMS) in general. 9 Other studies suggest that BCAAs may help preserve muscle in people on low carbohydrate diets. BCAAs help to promote the use of fatty acids for energy and enhance glycogen synthesis in the liver, thereby sparing muscle from being broken down as an energy source. 10 Recent studies suggest that BCAA intake may be inversely correlated with obesity in some individuals. In one study involving wrestlers, BCAA supplementation was more effective for reducing body fat than simple calorie restriction. 11 Other studies have looked at the potential to use plasma levels of BCAAs as a biomarker for the risk of type 2 diabetes and obesity, with some suggestion that levels of leucine may be elevated in people with insulin resistance. The reasons for this are unknown but may be related to increased absorption of the amino acid as an attempt to enhance glucose metabolism. Or, high leucine levels may be the result of some fault in leucine use leading to high circulating levels of the un-metabolized amino acid. Interestingly, a common variant of the protein phosphatase Mg2+/Mn2+ dependent 1K (PPM1K) gene, namely the rs1440581 T allele, has been related to elevated BCAA concentrations and risk of type 2 diabetes, and this allele was associated in a recent study with a poorer response to an energy-restricted diet. 12
BCAA side effects – short termBecause BCAAs are abundant in muscle tissue, it makes sense that greater muscle activity requires a greater intake of BCAAs. In other situations, however, different amino acids may be of greater benefit. For example, collagen contains very little of the BCAAs and instead is made up of large amounts of the amino acids glycine and proline. As such, BCAAs may offer little, if any, benefit for someone healing from an injury predominantly affecting connective tissue. In fact, a high BCAA intake at this time may prove detrimental to recovery because BCAAs could compete with proline and glycine for absorption. For the most part, BCAA supplements are safe and well tolerated, with few, if any, adverse effects. As mentioned earlier, it’s important to consult a health care practitioner prior to taking BCAAs if you have a kidney condition. People with type 2 diabetes should also consult a health care practitioner prior to taking BCAAs as they may affect how the body responds to insulin and uses glucose. 13
BCAA side effects – long term cancer risk?Are side effects associated with taking a BCAA supplement long term? Do BCAA supplements increase risk for cancer? There isn’t a definite answer as of yet, but some of the latest cancer and longevity research actually centers around amino acid restriction as a means of delaying aging and reducing the risk for cancers. Among the amino acids thought best to be consumed in limited amounts are the BCAAs as well as methionine and tryptophan, as these amino acids are thought to fuel the growth of cancer cells. 14 1
BCAA and mTORFor example, BCAAs cause activation of the mTORC1 pathway, which stimulates cells to grow and proliferate, including cancer cells, and amino acids like leucine have been isolated as carcinogenic in some animal models, as well as by longevity researchers like Dr. Valter Longo who is head of the Longevity Institute at the University of Southern California. 15 Also consider this study which showed that deprivation of leucine inhibits growth of breast cancer cells. To quote Dr. Longo:
The effect of AAs on the activation of the IGF-I and TOR-S6K pathways is likely to be an important factor in explaining the lifespan extension in AA restricted organisms and previous studies have noted benefits related to the restriction of particular AAs.Although we need some BCAAs in our diets, Dr. Longo’s research would seem to indicate that long term use of high dose BCAA supplements is probably a bad idea, and that these products should be reserved for performance athletes. For a nice rundown on the role of BCAAs in cancer growth, see Branch chain amino acids in cancer metabolism.