Background: A lack of understanding of the processes involved in the absorption and transfer of the ubiquinol form of Coenzyme Q10 has led to a situation in which incorrect marketing claims are being made for the absorption of ubiquinol supplements, possibly misleading physicians and patients in the selection of a Coenzyme Q10 supplement for heart health benefits.In clinical trials, the ubiquinone form of Coenzyme Q10 has been associated with significantly improved symptoms and survival in patients with heart failure and significantly improved heart function and reduced cardiovascular mortality in community-living senior citizens. The ubiquinone form is the more stable and more extensively researched form. The ubiquinol form is unstable by virtue of being an electron donor that is easily oxidized to the ubiquinone form. Nevertheless, insufficiently documented marketing claims are being made for ubiquinol supplements.

Methods: To investigate whether or not oral ubiquinol from supplements is absorbed in the ubiquinol form or ubiquinone form, our labs conducted 2 studies of the instability of ubiquinol supplements: a lab study of 13 ubiquinol products sold in the United States and an in vivo study of ubiquinol absorption in large dogs.

Results: In the lab study, 76% to 84% of the oral ubiquinol in the nutritional supplements was oxidized to ubiquinone at body temperature in an 8.2 pH solution simulating small intestinal juice. That is to say, much of the oral ubiquinol had been converted to ubiquinone in the sort of pH environment that it would encounter prior to absorption. In a similar fashion, the percentage of ubiquinol converted to ubiquinone increased as the capsule contents passed through the stomach and small intestines of the study dogs.

Conclusions: Based on the data from the lab study and the large dog study, we concluded that ubiquinol in commercial nutritional supplements will most likely be oxidized to ubiquinone before it reaches the absorption cells and that the Coenzyme Q10 in the ubiquinol supplements will be absorbed predominantly in the ubiquinone state, transfer into the lymph nodes predominantly in the ubiquinone state and be reduced back to ubiquinol in the lymphatic system.