A common bodybuilding and athletic performance enhancer contains an antioxidant that could damage heart and lungs, according to an article in the September issue of Journal of Clinical Investigation.

Researchers at the University of Virginia found that N-acetylcysteine (NAC), an antioxidant commonly used in nutritional and body-building supplements, tricks blood vessels into thinking they are oxygen-deprived, ultimately leading to pulmonary arterial hypertension (PAH).
Specifically, a NAC byproduct called nitrosothiol masks the true oxygen content of the blood. This, in turn, causes the arteries to become narrow, increasing the blood pressure in the lungs and producing swelling in the heart, said lead researcher Ben Gaston, MD, PhD.

After mice were given NAC and nitrosothiol for 3 weeks, red blood cells converted the compound into the nitrosothiol, S-nitroso-N-acetylcysteine (SNOAC). The normal mice that received NAC and SNOAC developed PAH. As a control, mice that were missing the endothelial nitric oxide synthase enzyme did not convert NAC to SNOAC, and were protected from the adverse effects of NAC, but not SNOAC. This suggests that NAC must be converted to SNOAC to cause PAH.

As the process applies to humans, co-researcher Lisa Palmer, MD, PhD, said tests would need to be developed to determine at what point antioxidant use becomes detrimental to the heart and lungs. Moreover, the results obtained in the current trials could be applied toward new ways of treating PAH the researchers said.

To read the abstract, click here.