Neither classed as a vitamin or mineral, Coenzyme Q-10 (C0Q10 for short) is a naturally occurring biochemical which can be found in every cell of our bodies.
It was first discovered in 1957 and during the early 70's interest was piqued when research suggested CoQ10 may help to treat a number of chronic ailments.
Since then, and not surprisingly, it's been awarded a list of superlatives by the supplement companies that sell it. But is supplemental CoQ10 really an elixir of youth and does it offer anything for those simply wanting to improve their overall health and fitness?
CoQ10 can be obtained from our diets or from supplements but it is also made endogenously (meaning it can be created inside the body without external sources). It plays a crucial role in cellular energy production, normal cardiac function and stimulates the immune system. Classed as an antioxidant, CoQ10 levels in our bodies reduces as we age, peaking at around age 20.
CoQ10 has been studied in a number of people with different chronic ailments. Some of the results of these studies have found that individuals with diseases such as congestive heart failure, diabetes and Parkinson's disease, high blood pressure and breast cancer have low levels of CoQ10.
Of course, the presence of low levels may not be causative of these illnesses (it could be the other way round) so what happened when researchers administered supplemental CoQ10 to these people?
A study of 424 patients suffering from a range of cardiovascular diseases found that were benefits from supplementing with CoQ10 . When looking at specific types of cardiovascular disease results have been even more interesting...
For people with congestive heart failure, taking 2mg per kilogram of bodyweight per day over the course of a year resulted in fewer cases of pulmonary oedema and cardiac asthma, as well as fewer hospital admissions .
When a group of 8 studies was analysed by Soja and colleagues, they concluded that heart failure patients supplementing with CoQ10 had improved physiological markers such as stoke volume (the amount of blood pumped in one beat), ejection fraction (the proportion of blood pumped out of the heart compared to the amount left in) and cardiac output (the amount of blood pumped by the heart in one minute) .
Other positive findings include: reduced systolic blood pressure with 120mg per day of CoQ10 in those suffering with hypertension [4,5] and a reduction in angina pain, arrhythmias (irregular heart beat) and heart attacks in individuals with ischaemic heart disease .
It's important to note that some studies have found no benefit from taking CoQ10. Despite CoQ10 levels in the blood increasing following supplementation of up to 200mg per day for 6 months, no improvements in ejection fraction, cardiac output, exercise duration and quality of life measures were found [7,8].
As well as some encouraging results in people with heart disease, CoQ10 has also lead to improvements in patients with early Parkinson's disease.
One study of 80 patients taking either 300mg, 600mg or 1200mg per day found that the 1200mg per day group showed significant improvements .
CoQ10 may also have a positive on effect on the frequency and severity of migraines , breast cancer, type 2 diabetes  and Huntingdon's chorea .
Because C0Q10 plays an important role in energy production, it led to speculation that it may improve athletic performance.
This proposition was initially tested using a group of cyclists and triathletes over a four-week period . Unfortunately, by the end, there was no evidence to support the theory.
In a follow up study using higher doses over a longer period of time, 100mg per day of CoQ10 was given to 10 cyclists over eight weeks . There was also no effect found by this study on their performance, nor were there any notably improved fitness levels. Various other studies were performed using other vitamins, doses and time frames – also with no positive results [15,16].
Conversely, when CoQ10 was given to a group of healthy men with an average age of 45, the results did show an increase in energy levels, although their levels of performance were still unchanged . Researchers think that the energy levels were affected perhaps because the CoQ10 created an anti-depressant effect, on account of its fat-soluble properties (which allow it to be absorbed into the nervous system).
A Finnish study was one of a few which showed an improvement in the performance of professional cross-country skiers, who took CoQ10 supplements and placebos . Those that used the coenzyme showed an improvement in overall aerobic fitness.
From current research there seems to be very little evidence to support CoQ10 supplementation as an ergogenic aid - but what about its effect on recovery from muscle damage?
One study on marathon runners showed that CoQ10 combined with vitamin E had no effect on reducing the amount of muscle damage to the runners . In fact, another study showed that taking CoQ10 during intense exercise can actually increase muscle damage . Even the placebo group in this Swedish study outperformed the athletes taking the CoQ10 supplements!
Researchers have concluded that if your body is very low on oxygen, such as during a sprint, or other high intensity exercise, CoQ10 acts in reverse as a pro-oxidant, and promotes damage to the cells.
To conclude, the evidence in favour of using CoQ10 to improve exercise performance is poor - and so at the moment it seems there really is no reason to shell out money for performance purposes.
It may however, turn out to be useful to middle aged men, if only for the purpose of relieving fatigue. Furthermore, it does show some promise in terms of other areas of health, such as improving conditions of heart disease, Parkinson's disease and diabetes.
CoQ10 has very low toxicity levels  for those who want to try it, but you should consult your doctor if you are currently taking medication as CoQ10 may interact with some of them.