The amino acid N-acetylcysteine – on sale in every drugstore as a component of cough medicine – not only has a broad antioxidant effect, but also enhances endurance performance, write researchers at the Chiang Mai University, Thailand, in Oxidative Medicine and Cellular Longevity.
N-Acetylcysteine [formula below left] is a building block for the small but important protein glutathione [formula below right]. Glutathione helps enzymes to detoxify cells. In experiments in which people were given 600 mg N-acetylcysteine, synthesis of glutathione increased and the concentration of aggressive molecules in the blood decreased. These aggressive molecules can cause damage to the cells. That's why supplements containing N-acetylcysteine or glutathione are popular with longevity freaks.
Physical exertion also causes aggressive molecules to be released. This seems to be a healthy process, as long as it does not occur in extreme amounts. It stimulates the body to produce more protective enzymes. This is the mechanism through which exercise probably protects the body against cancer and delays aging.
But the production of aggressive molecules during exercise reduces the functioning of muscle cells, and therefore puts a damper on performance. The researchers therefore wanted to know whether supplementation with N-acetylcysteine could protect muscle cells during exertion, and thus also improve performance.
The researchers gave 16 men a daily dose of 1200 mg N-acetylcysteine for a week. The men took one dose of 600 mg twice a day with their meals. The preparation they used was Fluimucil 600, produced by Zambon of Switzerland. A control group of 13 men took a placebo. The men were not physically active.
Before the supplementation started, and at the end of the period, the men had to move on a treadmill for 21 minutes. The researchers gradually increased the level of exertion every three minutes, until the men’s heart rate had reached about 85 percent of their maximum.
In the N-acetylcysteine group the VO2 max rose by a statistically significant amount of 7 percent. Moreover, after the supplementation period, the exertion level for the men in the N-acetylcysteine group was less tiring than it had been previously – and, yes, the effect was also statistically significant.
N-Acetylcysteine did not have an effect on classic catabolic markers such as TNF-alpha or creatine kinase. The amino acid did reduce the lactic acid concentration [Lactate].
In other experiments in which non-athletes do exercise, supplementation with classic antioxidants such as vitamin C and vitamin D inhibits the positive effects of intensive exercise. [By the way, not all studies show this – Ed.] The researchers don't exclude the possibility that N-acetylcysteine has a similar effect. They argue in favour of more research.