What are branched-chain amino acids (BCAAs)?

Overview

Branched-chain amino acids (BCAAs) are naturally occurring molecules (leucine,
isoleucine, and valine) that the body uses to build proteins. The term “branched
chain” refers to the molecular structure of these particular amino acids. Muscles
have a particularly high content of BCAAs. For reasons that are not entirely
clear, BCAA supplements may improve appetite in cancer patients and slow the
progression of amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease,
a condition that leads to degeneration of nerves, atrophy of the muscles, and
eventual death). BCAAs have also been proposed as a supplement to boost athletic
performance.

Requirements and Sources

Dietary protein usually provides all the BCAAs needed. However, physical stress and injury can increase a person’s need for BCAAs to repair damage, so supplementation may be helpful.

BCAAs are present in all protein-containing foods, but the best sources are red meat and dairy products. Chicken, fish, and eggs are excellent sources as well. Whey protein and egg protein supplements are another way to ensure that a person is getting enough BCAAs. Supplements may contain all three BCAAs together or simply individual BCAAs.

Therapeutic Dosages

The typical dosage of BCAAs is 1 to 5 grams (g) daily.

Therapeutic Uses

Preliminary evidence suggests that BCAAs may improve appetite in people undergoing treatment for cancer. There is also some evidence that BCAA supplements may reduce symptoms of amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease); however, not all studies have had positive results.

Preliminary evidence from a series of small studies suggests that BCAAs might decrease symptoms of tardive dyskinesia, a movement disorder caused by long-term usage of antipsychotic drugs. BCAAs have also shown a bit of promise for enhancing recovery from traumatic brain injury.

Because of how they are metabolized in the body, BCAAs might be helpful for
individuals with severe liver disease (such as cirrhosis).
BCAAs have also been tried for aiding muscle recovery after bedrest, such as
following surgery.

Although there is a little supportive evidence, on balance, current research
does not indicate that BCAAs are effective for enhancing sports performance. One
preliminary study hints that BCAAs might aid recovery from long-distance running.
BCAAs have also as yet failed to prove effective for muscular
dystrophy.

Scientific Evidence

Appetite in cancer patients. A double-blind study tested BCAAs on twenty-eight people with cancer who had lost their appetites because of either the disease itself or its treatment. Appetite improved in 55 percent of those taking BCAAs (4.8 g daily) compared with only 16 percent of those taking a placebo.

Amyotrophic lateral sclerosis (Lou Gehrig’s disease). A small double-blind study found evidence that BCAAs might help protect muscle strength in people with Lou Gehrig’s disease. Eighteen individuals were given either BCAAs (taken four times daily between meals) or a placebo and followed for one year. The results showed that people taking BCAAs declined much more slowly than those receiving a placebo. In the placebo group, five of nine participants lost their ability to walk, two died, and another required a respirator. Only one of the nine participants receiving BCAAs became unable to walk during the study period. This study is too small to provide conclusive evidence, but it does suggest that BCAAs might be helpful for this disease. However, other studies found no effect, and one actually found a slight increase in deaths during the study period among those treated with BCAAs compared with those treated with a placebo.

Muscular dystrophy. One double-blind, placebo-controlled study found leucine (one of the amino acids in BCAAs) ineffective at the dose of 0.2 g per kilogram body weight (for example, 15 g daily for a 75-kilogram woman) in 96 individuals with muscular dystrophy. Over the course of one year, no differences were seen between the effects of leucine and a placebo.

Safety Issues

BCAAs are believed to be safe; when taken in excess, they are simply converted
into other amino
acids. However, like other amino acids, BCAAs may interfere
with medications for Parkinson’s disease. They may reduce
the effectiveness of medications for Parkinson’s disease (such as levodopa).

Bibliography

Aquilani, R., et al. “Branched-Chain Amino Acids Enhance the Cognitive Recovery of Patients with Severe Traumatic Brain Injury.” Archives of Physical Medicine and Rehabilitation 86 (2005): 1729-1735.

Charlton, M. “Branched-Chain Amino Acid Enriched Supplements as Therapy for Liver Disease.” Journal of Nutrition 136 (2005): 295S-298S.

Crowe, M. J., et al. “Effects of Dietary Leucine Supplementation on Exercise Performance.” European Journal of Applied Physiology 97 (2006): 664-671.

Marchesini, G., et al. “Nutritional Treatment with Branched-Chain Amino Acids in Advanced Liver Cirrhosis.” Journal of Gastroenterology 35 (2000): 7-12.

Richardson, M. A., et al. “Branched Chain Amino Acid Treatment of Tardive Dyskinesia in Children and Adolescents.” Journal of Clinical Psychiatry 65 (2004): 92-96.

Richardson, M. A., et al. “Efficacy of the Branched-Chain Amino Acids in the Treatment of Tardive Dyskinesia in Men.” American Journal of Psychiatry 160 (2003): 1117-1124.

Stein, T. P., et al. “Branched Chain Amino Acid Supplementation During Bed Rest: Effect on Recovery.” Journal of Applied Physiology 94 (2003): 1345-1352.

Watson, P., et al. “The Effect of Acute Branched-Chain Amino Acid Supplementation on Prolonged Exercise Capacity in a Warm Environment.” European Journal of Applied Physiology 93 (2004): 306-314.