Ubiquinone is a naturally occurring part of the electron transport chain (ETC) in the mitochondria (power houses) of cells. It is also found within lipid membranes including the plasma membrane and intracellular membranes. Being a mobile part of the inner mitochondrial matrix where ATP is formed, its biological significance has been well studied.
In addition to its role as an electron carrier, it can also prevent oxidative damage to lipids. It has also been suggested that it can help regenerate vitamin E. Muscle concentrations of ubiquinone fall with age, various disease states (e.g., muscular dystrophy, congestive heart failure), and exercise. Thus, there has been research interest in bolstering endogenous levels via dietary means (in the form of vitamin Q).
Recent data reveal that supplementary Co-Q10 can increase tissue concentrations in humans after 14 days of supplementation and increase further after 28 days.
This research also showed that a combination of 100 IU of vitamin E + Co-Q10 appears to be the best way to maximize its tissue uptake (although vitamin E itself was incorporated in a dose-dependent manner up to 1300 IU).
The data are mixed regarding Co-QIO supplementation and performance with some studies showing benefit, some showing no benefit, and one showing greater muscular damage with supplementation.