A randomized cross-over study by supplementation with single doses of coenzyme O 1 0 (30 mg/person), administered either as a meal consisting of cooked pork heart or as 30 mg coenzyme Q 1 0 capsules was performed to investigate the bioavailability of dietary coenzyme Q 1 0 in humans. The increase in serum coenzyme Q 1 0 concentration was used as an index of the absorption, and reached a maximum six hours after the ingestion of either meal or capsules. Following intake of coenzyme Q 1 0 capsules, the serum coenzyme Q 1 0 concentrations increased significantly (p<0.01) from a baseline concentration at 0.88 to 1.19 mg/L. The pork heart meal resulted in a significant (p<0.01) increase in serum coenzyme Q 1 0 from 0.97 to 1.44 mg/L. The difference between the absorption from meal and capsules was not significant. This study indicates that coenzyme Q 1 0 present in the diet may contribute significantly to plasma coenzyme Q 1 0 concentrations in humans.