The new study, which involved 420 patients who had suffered heart failure, showed that those who took three 10mg tablets of CoQ10 a day had lower levels of heart failure two years later.

Fewer of the patients who had taken the supplement had died at the end of the study.

Professor Svend Mortensen, from the Heart Centre at Copenhagen University Hospital, who led the study, said: “The CoQ10 treated patients had reduced hospital admission rates for worsening heart failure and lower cardiovascular death, both of which may reflect a significant improvement in cardiac function.

“CoQ10 should be considered as a part of the maintenance therapy of patients with chronic heart failure.”

The results were presented at Heart Failure 2013 – the main annual meeting of the Heart Failure Association of the European Society of Cardiology – in Lisbon, Portugal.

It is also found in foods such as red meat and fish, but at very low levels that deemed to be insufficient to impact on heart failure.

The molecule is known to play an essential role in the mitochondria, the tiny power stations found inside almost every cell of the body that convert sugar into energy.

The new study, known as the Q-SYMBIO trial, followed patients in Denmark, Sweden, Austria, Slovakia, Poland, Hungary, India, Malaysia and Australia.

After two years, 14% of patients taking CoQ10 had suffered problems with their heart compared to 25% of those who had been taking a placebo.

Just 9% of the patients taking CoQ10 had died compared to 17% taking the placebo.

CoQ10 is currently sold over the counter at pharmacists, including Boots, as an energy booster.

Statins, one of the drugs taken by heart failure patients to control cholesterol, is also known to block the synthesis of CoQ10 in the body, causing levels to drop.

It is unclear how many of the patients in the study were taking statins and the CoQ10 could have been compensating for this effect in the study.

But Professor Mortensen said he hoped to conduct a trial to see how taking CoQ10 with statins could improve heart patient mortality rates compared to just taking statins alone.

He added: “Statins reduce CoQ10, and circulating CoQ10 prevents the oxidation of LDL effectively, so I think ischemic patients should supplement statin therapy with CoQ10.

Helen Williams, a consultant pharmacist for cardiovascular disease at NHS Southwark Clinical Commissioning Group and a member of the Royal Pharmaceutical Society, said: “this is a relatively small study for a cardiovascular trial.

“We have often been misled before by small studies that fail to show benefits when extended to larger numbers of patients, so I would great these results with cautious optimism.”

We believe that any positive trial is worth exploring and should not be dismissed in public before a larger clinical trial can take place.