The coenzyme is concentrated in the mitochondria - the 'power plants' of the cell - and 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.

The formulation of the CoQ10 is reported to play a key role in its bioavailability. Since the coenzyme is lipophilic (fat-loving) its absorption is enhanced in the presence of lipids. However, when taken as a supplement apart from meals, the absorption of some formulations is lower.

Trials with CoQ10 supplements in powder and oil-suspension forms are reported to result in small or negligible responses in plasma CoQ10 concentrations.

According to a review of CoQ10 by Hemmi Bhagavan and Raj Chopra from Tishcon Corporation in New York (Free Radical Research, Vol. 40, pp. 445-453), solubilised formulations elicit a large response.

The majority of research looking at the benefits for health conditions has focused on the cardiovascular diseases. Heart tissue contains the highest concentration of CoQ10 in the human body (about 132 nanomoles per gram), along with the kidney (77 nanomoles per gram) and the liver (64 nanomoles per gram).

There is an ever-growing body of scientific data that shows substantial health benefits of CoQ10 supplementation for people suffering from angina, heart attack and hypertension. Clinical trials have also reported benefits for cardiomyopathy and congestive heart failure.

CoQ10 concentration in the human brain is reported to be only 15.5 nanomoles per gram, a relatively low concentration that is linked to the high rate of oxidative stress in this organ. For this reason, researchers are increasingly looking at the possible protective role of CoQ10 in the development of neurodegenerative diseases such as Parkinson's and Alzheimer's.

Indeed, a recent study in the journal Behavioural Brain Research (doi: 10.1016/j.bbr.2006.03.009) investigated the effects of supplementation of the diets of rats suffering from brain impairment by oxidative stress, presented as a model for Alzheimer's.

The researchers reported a significant improvement in the loss of cognitive function, leading them to conclude that CoQ10 could play a role in the prevention of this disease.

And this highlights an important consideration with animal studies concerning CoQ10. While rats are extensively used for preliminary tests, it should be mentioned that guinea pigs might be more reliable models. The major form of coenzyme Q in rats is CoQ9, and not CoQ10 like in humans, and guinea pigs.

The benefits of CoQ10 are also being explored in relation to other conditions and diseases. Studies are emerging linking supplements of coenzyme to benefits for diabetes, cancer (breast, lung and prostate), male infertility, and kidney failure.

Clinical trials looking at the effects of coenzyme Q10 are on-going around the world, with research reported in countries such as the USA, Norway and Ecuador.

A list of on-going trials is presented below.