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Supplement Guide: Branched-Chain Amino Acids

Improve exercise performance and reduce muscle breakdown

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Where it comes from: Branched-chain amino acids are essential amino acids (specifically, valine, leucine and isoleucine). "They are essential, meaning we must get them in our diet because our bodies do not produce them," explains Sarah Currie, RD and personal trainer for New York City-based Physical Equilibrium LLC. "The term 'branched-chain' just refers to the molecular structure." Amino Acids are the building blocks of protein (think: meat, dairy and legumes) and have various functions related to energy production during and after exercise so they are needed in adequate amounts, but not excessive.

What it'll do for you: Branched-chain amino acids are often used to treat Lou Gehrig's disease, brain conditions due to liver disease, elderly and cancer patients and people who are confined to bed rest. Some perfectly healthy people use BCAAs to prevent fatigue and improve concentration. But the most relevant to you, perhaps, is the common practice of taking branched-chain amino acids to improve exercise performance and reduce muscle breakdown. While the first use has a fair amount of skeptics, the second is widely accepted in the medical world.

  • Improving exercise performance
    Exercise causes an increase in serotonin levels, which are believed to cause fatigue. But BCAAs are believed to reduce serotonin levels, and thus cancel out the fatigue and actually enhance exercise performance. There have been many studies that promote this exact ability: In 1998, subjects ingested either BCAA or a placebo before taking an endurance cycle ride in the heat. The BCAA group cycled 153.1 minutes on average, while the placebo group averaged only 137 minutes. A more recent Japanese study looked at the effects of a BCAA mixture on athletes during a one-month training stint and found that indices of blood oxygen-carrying capacity were increased. However, many other studies indicate that BCAAs have no improvement and the amino acids are said to be ineffective for this use.
  • Reducing muscle breakdown
    "BCAAs are metabolized primarily in skeletal muscles, while other amino acids are metabolized in the liver, which is why some think they must take BCAA supplements if they're engaging in strenuous exercise," explains Currie. With that in mind, BCAAs are often touted to help repair damaged muscles, decrease muscle soreness and increase muscle function. Some data shows that BCAA supplementation before and after exercise has beneficial effects for decreasing exercise-induced muscle damage and promoting muscle-protein synthesis. A 2006 study concluded that the intake of BCAA may promote an anabolic hormone profile (causing muscle repair after workouts) while also decreasing the likelihood of training-induced muscle damage. A Japanese study examined a group of men and women—some given BCAA supplements and others given a placebo—as they did multiple testing days involving squats, which were used to promote delayed muscle soreness. Both sexes reported less soreness when they were given the supplements. Studies like this one and many others lead experts to believe it's possible to consider BCAA as a useful supplement for muscle recovery.

Suggested intake: The body obtains branched-chain amino acids from proteins found in food, especially meat, dairy products and legumes. "A balanced diet with adequate protein provides enough BCAAs, even for the strenuous exerciser," says Currie. Nitrogen balance studies have shown that no amount above 2.0 grams per kilogram of body weight is beneficial. And just because experts believe BCAAs help prevent muscle breakdown doesn't mean it's necessary. Says Currie: "As long as you're getting enough dietary macronutrients—such as proteins, fat and carbohydrates—lean body mass, or muscle, will be spared." If you do decided to take BCAA supplements, make sure they're from a reliable company. "Also, pay attention to how you feel while taking them," warns Currie. "If you think they're makes a difference, go for it."

Associated risks/scrutiny: Branched-chain amino acids appear to be safe for most people when used for up to six months. Side effects may include fatigue and loss of coordination.

"In healthy people, excess protein hasn't been proven to be harmful," Currie explains. "Athletes on high protein diets should stay well-hydrated, as water loss can be increased from nitrogen excretion during protein breakdown."

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