(See also Overview of Dietary Supplements.)
Coenzyme Q10 (CoQ10, ubiquinone) is an antioxidant, produced naturally in humans, that is also a cofactor for mitochondrial ATP generation. The levels of CoQ10 seem to be lower in older people and in people with chronic diseases, such as cardiac problems, cancer, Parkinson disease, diabetes, HIV/AIDS, and muscular dystrophies. However, it is not known whether these low levels contribute to these disorders. Rich dietary sources are meat, fish, and vegetable oils. Most trials recommended that the supplement dose range between 100 and 300 mg/day (eg, 100 mg tid).
CoQ10 is said to be useful because of its antioxidant effect and role in energy metabolism. Specific claims include an anticancer effect mediated by immune stimulation, decreased insulin requirements in patients with diabetes, slowed progression of Parkinson disease, efficacy in treatment of heart failure, and protection against anthracycline cardiotoxicity. The most prominent claim may be ameliorating endothelial cell dysfunction that contributes to cardiovascular disease. Although some preliminary studies suggest CoQ10 may be useful in treating these disorders, results are unclear and more testing is needed.
A 2012 meta-analysis evaluated 5 randomized, controlled trials with a total of 194 patients and found a significant improvement in endothelial function, as measured by flow-mediated peripheral arterial dilation (1). A 2013 meta-analysis of randomized controlled trials suggested that CoQ10 may improve functional status in patients with heart failure (2). However, this meta-analysis consisted of trials mainly of small size and short duration of treatment.
A 2014 randomized, controlled, multicenter study of 420 patients with heart failure showed that CoQ10, 100 mg po tid, when added to standard therapy, was safe, relieved symptoms, and reduced major cardiovascular events (3). In these meta-analyses, the doses and target blood levels of CoQ10 were not standardized, a further limitation.
Gao L, Mao Q, Cao J, et al. Effects of coenzyme Q10 on vascular endothelial function in humans: a meta-analysis of randomized controlled trials. Atherosclerosis 221(2):311-316, 2012.
Fotino AD, Thompson-Paul AM, Bazzano LA. Effect of coenzyme Q10 supplementation on heart failure: a meta-analysis. Am J Clin Nutr 97(2):268-275, 2013.
Mortensen SA, Rosenfeldt F, Kumar A, et al. The effect of coenzyme Q10 on morbidity and mortality in chronic heart failure results from Q-SYMBIO: a randomized double-blind trial. JACC Heart Fail 2(6):641-649, 2014. doi:10.1016/j.jchf.2014.06.008
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