In a study involving 51 patients having at least 50% stenosis of one major coronary artery (assessed via cardiac catheterization) and 102 healthy controls, significantly lower plasma coenzyme Q10 levels were found in subjects with CAD, as compared to controls. Furthermore, lower levels of the antioxidant enzymes, catalase (CAT), and glutathione peroxidase (GPx) and higher levels of plasma malondialdehyde and superoxide dismutase (SOD) were found in patients with CAD as compared to controls. Plasma coenzyme Q10 was positively associated with CAT and GPx activities and negatively correlated with MDA and SOD. The authors conclude, “A higher level of plasma coenzyme Q10 (>=0.52 micro mol/L) was significantly associated with reducing the risk of CAD. Our results support the potential cardioprotective impact of coenzyme Q10.”