Ubiquinol

CoQ10 exists in two states: oxidised ubiquinone and reduced ubiquinol. Ubiquinol is marketed as the "active" form that absorbs better. The evidence on that is split. In 12 healthy volunteers taking 200 mg a day for four weeks of each form, ubiquinol raised plasma CoQ10 to 4.3 µg/mL against 2.5 µg/mL for ubiquinone [1]. In a randomised crossover in 21 healthy adults aged 65 to 74, ubiquinol's 1.7-fold advantage over ubiquinone was not statistically significant. A water-soluble ubiquinone syrup beat both [2].

Its most notable clinical result is in multiple-system atrophy, a rare neurodegenerative disease. In a randomised phase 2 trial of 139 patients, high-dose ubiquinol met its primary endpoint, a motor score, and improved daily-living and walking measures, with side-effect rates similar to placebo [3]. Smaller trials found that ubiquinol raised CoQ10 levels in septic shock without changing clinical outcomes [4]. In trained adults it reduced oxidative damage markers from strenuous exercise [5].

Ubiquinol is the reduced form of CoQ10 [1]. After strenuous exercise it raised fat-soluble antioxidant status and lowered oxidative damage markers [5]. Taking ubiquinol raised the share of blood CoQ10 in the reduced state, and taking ubiquinone did not [1].

No side effects were noted in the head-to-head bioavailability study [1]. In the multiple-system atrophy trial, adverse events possibly related to the drug were no more common than on placebo [3].