The strongest evidence for CoQ10 lies in cardiovascular disease: multiple randomised trials and meta-analyses show a reduction in mortality and risk factors, particularly in heart failure patients using ubiquinone. The claim that CoQ10 boosts energy in healthy people is far less well supported and rests primarily on early, small-scale research. CoQ10 is safe at customary doses, but those most likely to benefit are people with a cardiovascular condition, not the average healthy person looking for more energy.
CoQ10 (coenzyme Q10) is a substance the body produces on its own that plays a key role in energy production within the mitochondria, the cell's power plants. CoQ10 also acts as an antioxidant: it protects cell membranes and fat particles in the blood from damage caused by oxygen radicals. That dual function makes it an interesting compound in cardiovascular disease, where mitochondrial dysfunction and oxidative damage play a central role. Supplementation demonstrably raises blood levels, but uptake into tissues is limited by the compound's poor solubility; special formulations improve this to some extent.
The evidence is most fully developed for the heart. A meta-analysis of randomised trials1 showed that CoQ10 supplementation reduced all-cause mortality in people with cardiovascular disease by approximately 32% (relative risk 0.68; confidence interval 0.49-0.94). The confidence interval is wide, which calls for some caution, but the direction is consistently positive. That same meta-analysis also finds moderate to strong support for CoQ10 reducing cardiovascular risk factors such as blood pressure, blood lipids and inflammatory markers.
Specifically in heart failure, a review of 28 clinical trials2 shows that CoQ10 in its oxidised form, ubiquinone, reduced cardiovascular mortality and hospital admissions in heart failure patients. Notably, this effect was not found for ubiquinol, the reduced form that is sometimes promoted as 'superior'. It is worth mentioning here that one of the authors of that review is employed by a company that manufactures CoQ10 products; this represents a potential conflict of interest when interpreting the results.
For energy in healthy people or older adults, the evidence is considerably thinner. There are indications that CoQ10 may alleviate complaints associated with ageing and with rare mitochondrial diseases, but this research is still at an early stage and large-scale, well-designed trials are lacking3. The widely heard claim that CoQ10 'gives energy' to healthy people is therefore not well supported by clinical studies.
The picture on safety is clear: no serious side effects have been reported at customary supplementation doses. CoQ10 is considered one of the better-tolerated supplements. Finally, the idea that CoQ10 helps in Alzheimer's disease has been raised in a nutritional review, but clinical evidence is entirely absent; this is insufficient to expect anything from it.
Evidence based on PMIDs 36480969 (meta-analysis of RCTs, mortality and risk factors), 37971634 (review of 28 trials in heart failure, note author conflict of interest), 34129891 (review of ageing/mitochondrial deficiency), 24389208 and 16551570 (mechanism, absorption and safety), 36555691 (oxidative damage in heart cells, preclinical), 33882663 (nutritional review Alzheimer's, narrative/insufficient evidence).