Amino acids are often called the building blocks of proteins, which help your body perform essential functions such as growth, digestion, and tissue repair. Your body naturally produces 11 amino acids, while the other nine—known as “essential” amino acids—must come from protein-rich foods like meat, eggs, and dairy.
Supplements are another option, and they’re popular among people looking boost their fitness. Studies on their effectiveness are limited, but here are three things that could happen to your strength and exercise performance when you take amino acid supplements.
There’s little evidence that amino acid supplements alone will make your muscles bigger. If you’re already meeting your daily protein needs through whole, healthy foods, you’re already consuming the amino acids needed to support muscle growth, said Anthea Levi, MS, RD, a dietitian and founder of ALIVE+WELL Nutrition. In that case, taking a supplement is unlikely to provide additional benefit—unless you are training at a high intensity, added Emily Hernandez, MS, ACSM, a certified exercise physiologist at Orlando Health.
That said, some research suggests that taking a daily dose of branched-chain amino acids (BCAAs)—leucine, isoleucine, and valine—about 30 to 45 minutes after resistance exercise may temporarily stimulate muscle protein synthesis, the process by which muscles repair and grow. This effect is thought to occur through activation of the mTORC1 pathway, which helps trigger muscle-building processes, Levi explained.
Though the evidence isn’t conclusive, amino acid supplements—particularly BCAAs—may help reduce fatigue during long or intense workouts, Hernandez said. One small clinical trial found that combining moderate exercise with BCAA supplementation for eight weeks improved strength, mobility, and endurance in older adults.
During exercise, muscle tissue develops small microtears that promote growth over time. Some clinical trials indicate that BCAAs may help alleviate soreness during this process, which could be especially helpful for those who are new to exercise or regularly training at high intensity, Hernandez said. Other studies, mostly in animals, hint that taking the amino acid glutamine—the most abundant amino acid in the body—may also help with soreness.
Even so, it’s important to remember that no supplement can replace a balanced, high-quality diet, Hernandez emphasized.
Experts recommend speaking with a healthcare provider before taking amino acid supplements. In most cases, they aren’t necessary if you’re already meeting your daily protein needs through diet, Levi said. High-protein foods rich in amino acids include lean meats like chicken and turkey, soy, nuts, seeds, beans, and fish such as salmon and tuna.
Amino acid supplements are generally well-tolerated, said Shannon O’Meara, MS, RD, LDN, a dietitian with Orlando Health. Those most likely to benefit are people new to exercise, individuals who train at high intensities, and older adults who may be experiencing age-related muscle loss, Hernandez said.
That said, amino acids aren’t appropriate for everyone. Children, pregnant or nursing women, and those with underlying health conditions like diabetes or liver disease should avoid these supplements. Possible side effects include:
- Nausea
- Diarrhea
- Muscle cramps
- Dehydration
- Headaches
- Confusion
- Liver and kidney complications
Because dietary supplements aren’t regulated by the U.S. Food and Drug Administration, experts recommend choosing products that have been third-party tested for purity and label accuracy by organizations such as the U.S. Pharmacopeia (USP) or the National Sanitation Foundation (NSF).
