Amino acids are chemicals that are used to synthesize proteins in the body. Mixtures of specific amino acids known as branched-chain amino acids are sometimes recommended for MS. There is no evidence that people with MS are deficient in amino acids or that amino acid therapy is beneficial for MS. Inconsistent results have been obtained in studies of the effects of branched-chain amino acid use on mental and physical performance in athletes. Importantly, high doses (greater than 20 grams daily) may produce fatigue by increasing the amount of ammonia in the blood.
One specific amino acid, threonine, has been studied in people with MS who have muscle stiffness, or spasticity. Research suggests that threonine improves stiffness as measured by formal clinical testing. However, this effect is so mild that it is not noticeable to people taking the compound. Thus, threonine does not appear to be effective enough to consider its use for MS-associated spasticity.