Coenzyme Q-10 is an important rate-limiting nutrient that is a cofactor in the mitochondrial electron transport chain, the biochemical pathway in cellular respiration from which adenosine triphosphate (ATP) and metabolic energy is derived. Since nearly all cellular activities are dependent upon energy, coenzyme Q-10 is essential for the health of all human tissues and organs, especially the heart. Given the strength of the science that has been emerging for the use of supplemental CoQ10, it is important to ensure that optimal CoQ10 levels are achieved in the blood following supplementation. Biochemically, it functions much like vitamin E in that it participates in certain antioxidant and free radical reactions. Numerous studies indicate coenzyme Q-10 also plays an important role in the maintenance of the entire cardiovascular system. Coenzyme Q-10 is also important for the maintenance of blood vessels and heart muscle function. In addition, people taking statin drugs can develop deficiencies in coenzyme Q-10 and may require supplementation.