Bioavailability of Coenzyme Q: An Overview of the Absorption Process and Subsequent Metabolism.

A lack of understanding of the processes determining the absorption and subsequent metabolism of coenzyme Q (CoQ) has resulted in some manufacturers' making incorrect claims regarding the bioavailability of their CoQ supplements, with potential consequences for the use of such products in clinical trials. The purpose of the present review article is, therefore, to describe the various stages of exogenous CoQ metabolism, from its first ingestion, stomach transit, absorption from the small intestine into the lymphatic system, transport in blood, and access into cells. In particular, the importance of CoQ crystal dispersion in the initial formulation is emphasised, the absence of which reduces bioavailability by 75%. In addition, evidence comparing the relative bioavailability and efficacy of ubiquinone and ubiquinol forms of CoQ has been reviewed.