Supplements of coenzyme Q10 may boost physical performance and reduce feelings of tiredness associated with exercise, Japanese researchers have reported.

Both fatigue and recovery time were decreased as a result of 300 milligrams of CoQ10 for eight days, according to the double-blinded, placebo-controlled study with 17 healthy volunteers published in the journal Nutrition.

"We found that oral administration of 300 mg of coenzyme Q10 for 1 wk improved physical performance during fatigue-inducing workload trials on a bicycle ergometer," wrote lead author Kei Mizuno.

"However, this positive result was not seen in the group administered 100 mg of coenzyme Q10."

CoQ10 has properties similar to vitamins, but since it is naturally synthesized in the body it is not classed as such. With chemical structure 2,3-dimethoxy-5-methyl-6-decaprenyl-1,4-benzoquinone, it is also known as ubiquinone because of its 'ubiquitous' distribution throughout the human body.

The level of CoQ10 produced by the body begins to drop after the age of about 20, and the coenzyme is concentrated in the mitochondria - the 'power plants' of the cell. It plays a vital role in the production of chemical energy by participating in the production of adenosince triphosphate (ATP), the body's co-called 'energy currency'.

A role beyond the mitochondria is also acknowledged, with CoQ10 acting as a potent antioxidant. The coenzyme plays an important role in preserving levels of vitamin E and vitamin C.

Researchers from Osaka City University Graduate School of Medicine, Soiken Incorporation, Kansai University of Welfare Sciences, and Osaka University of Foreign Study, recruited the 17 volunteers (average age 37.5) and randomly assigned them to receive daily coenzyme Q10 supplements (100 or 300 mg, Kaneka Corporation) or placebo for eight days. All subjects underwent the three interventions, with washout periods separating the eight-day long studies.

Physical performance, tested using a bicycle ergometer at fixed workloads, was found to increase when the subjects received the 300 mg CoQ10 dose, compared to the lower dose CoQ10 group and the placebo group.

Furthermore, subjective fatigue sensation in the high dose CoQ10 group was "alleviated when compared with that in the placebo group," wrote the researchers.

According to background information in the article, fatigue, which can occur in both healthy and ill people, is "best defined as difficulty in initiating or sustaining voluntary activity and can be classified into mental and physical fatigue."

Commenting on the potential mechanism, the Japanese researchers wrote: "Exercise-induced reductions in energy substrates, reactive oxygen species, and protein oxidation are thought to be associated with physical fatigue. Coenzyme Q10 is a vitamin-like, lipid-soluble compound existing in all cells. It is an indispensable compound in the respiratory chain of the inner mitochondrial membrane and acts as an essential antioxidant assisting in the regeneration of other antioxidants

"Therefore, administration of coenzyme Q10 may attenuate physical fatigue through its functions as an antioxidant or in assisting oxidative phosphorylation."

Public demand for products containing CoQ10 has seen the market grow. In the United States most new CoQ10 products have been supplements, with fewer skin care products hitting the market.

In Europe, CoQ10 has proved more popular in skin care formulations than in supplements, thanks to its anti-aging antioxidant properties.

Conservative estimates put worldwide sales of CoQ10 at around $350 million in 2004.

Source: Nutrition (Elsevier)
Published online ahead of print 13 February 2008, doi:10.1016/j.nut.2007.12.007
"Antifatigue effects of coenzyme Q10 during physical fatigue"
Authors: Kei Mizuno, M. Tanaka, S. Nozaki, H. Mizuma, S. Ataka, T. Tahara, T. Sugino, T. Shirai, Y. Kajimoto, H. Kuratsune, O. Kajimoto, Y. Watanabe