Is NAC an undetectable athletic performance enhancer?
N-acetylcysteine (NAC) has been extensively studied, mainly for its ability to replenish levels of intracellular glutathione, the body’s “master antioxidant”, probably more important than any antioxidant that can be ingested in food. NAC does this by supplying cysteine, an amino acid which is the rate-limiting constituent in glutathione biosynthesis. Cysteine is normally present in protein-rich foods, especially animal proteins, but it is in both short supply when one wants glutathione levels to increase, and it can’t be taken separately, since it can be toxic and won’t properly enter the cells where it’s needed either. NAC overcomes both of these problems: it’s relatively non-toxic, and is taken up by cells and de-acetylated to form cysteine, which can then be used in glutathione synthesis.Depletion of glutathione levels is a cause, an indicator, or both, of fatigue due to exercise. It’s been shown clinically that administration of NAC does indeed raise glutathione levels, and now, it’s been shown that, in trained athletes, NAC increases time to fatigue by an astonishing 23%.
In the cited study, fairly massive amounts of NAC were infused intravenously during exercise, which might lead one to doubt the practicality of using it to enhance athletic performance. However, another study — one of many that could be cited — Effect of N-acetyl-cysteine on the hypoxic ventilatory response and erythropoietin production: linkage between plasma thiol redox state and O2 chemosensitivity, found that very modest doses of NAC, 200 mg three times daily, massively increased erythropoeitin production and increased the hypoxic ventilatory response.