Every time you exercise your body generates oxidative stress as a natural byproduct of muscle contraction and energy production. At moderate levels that is a healthy signal. But when exercise intensity exceeds N acetylcysteine supplementation increases exercise performance and reduces oxidative stress only in individuals with low levels of glutathione ScienceDirect Glutathione and Vitamin C supplement combo enhances athletic performance, new trial shows Optimal Health Insider Optimal Health Systems Glutathione and Vitamin C supplement combo enhances athletic performance, new trial shows Optimal Health Insider Optimal Health Systems