The Instability of the Lipid-Soluble Antioxidant Ubiquinol: Part 2-Dog Studies

Coenzyme Q10 is one of the most widely sold nutritional supplements in the United States. Coenzyme Q10 is available in both its oxidized form (ubiquinone) and its reduced form (ubiquinol). The predominant marketing of Coenzyme Q10 to physicians and patients asserts that the ubiquinol form of Coenzyme Q10 has superior absorption to the ubiquinone form. This study has been designed to compare and contrast the stability and absorption of ubiquinol supplements, as well as the claims made for ubiquinol compared with ubiquinone.Ubiquinol, the reduced state of Coenzyme Q10, is commercially available as a nutritional supplement; however, ubiquinol, by its nature as an electron donor, is much less stable than ubiquinone, the oxidized state of Coenzyme Q10. The absorption, bioavailability and efficacy of ubiquinol products has been much less often tested in clinical trials. Consequently, insufficiently documented marketing claims are being made for ubiquinol supplements.

In Part 1 of this report on the instability of the lipid-soluble antioxidant ubiquinol, SIBR Research presented data from lab studies showing that oral ubiquinol is likely to be oxidized to ubiquinone and absorbed as ubiquinone. In this Part 2, SIBR Research conducted a study of the transfer and absorption of orally ingested ubiquinol in large dogs.

In the dog studies, the percentage of ubiquinol converted to ubiquinone increased as the capsule contents passed through the stomach and small intestines and into the lymph system.

The dog studies demonstrate that oral ubiquinol in commercial nutritional supplements is not stable in the gastrointestinal tract of large dogs. Based on these results, it seems likely that in humans also, most of the ubiquinol from capsules will be oxidized to ubiquinone in the acid profile between the stomach and the small intestines, where there is a wide range of acidity. The ubiquinol from the supplement will be absorbed in the ubiquinone state and will pass into the lymph system as ubiquinone, where it will be reduced back to ubiquinol. It will pass from the lymph system into the blood circulation as ubiquinol.