Paracetamol, one of the world’s most widely taken painkillers, may boost memory.
Researchers believe it acts on key brain cells that control recall, and have now begun a clinical trial.
It follows a pilot study by the same team whose as yet unpublished results show people taking daily paracetamol performed better on memory tests.
The average Briton takes 106 paracetamol tablets each year, usually to lower fever or relieve mild to moderate aches and pains.
Scientists believe its pain-killing properties stem from the ability to reduce the number of chemicals in the body called prostaglandins.
These are released in response to illness or injury, and are thought to sensitise nerve endings to feelings of pain and physical discomfort.
Experts believe that paracetamol blocks the activity of an enzyme called cyclooxygenase-2, which stops production of these pain-causing prostaglandins.
In addition to this, laboratory studies also show paracetamol triggers the release of the feel-good brain chemical serotonin, which as well as boosting its pain-relieving benefits, can have an indirect effect on memory, by reducing feelings of stress (which can affect memory).
More directly, paracetamol is also thought to activate an area of the brain involved in learning, memory and problem-solving called the hippocampus.
However, scientists are still unclear of the exact mechanism through which it works, and some early stage animal studies have shown that at low doses paracetamol may actually hamper memory.
But when used at high doses the drug is thought to produce beneficial effects.
A recent Swedish study showed that agitation levels in people with dementia reduced by 17 per cent over an eight-week period when treated with high-dose paracetamol.
In the new memory trial, which started last month, scientists at the University Hospital Clermont-Ferrand, France, will ask 44 healthy men and women to take a daily dose of 2g paracetamol, the equivalent of four tablets, for nine months (the maximum daily safe dose of paracetamol is 4g).
Reaction times and decision-making skills will be analysed throughout this time, and the volunteers will also be asked to sit memory tests. The scientists will monitor the subjects’ overall health to check for adverse effects.
The trial follows a recently completed study by the same team, with 40 men and women, which the researchers say showed a memory improvement with daily paracetamol, but there was no placebo group.
The new trial will have a placebo group, and neither the patients nor the investigators will know who has been given the real drug or a dummy pill until after the trial is completed.
Commenting on the study, Dr Anne Corbett, research manager at charity The Alzheimer’s Society, said: ‘The problems caused by dementia can mean much more than simply misplacing keys or forgetting a phone number. It can mean not being able to recognise family or where you live.
‘It is therefore vitally important that we develop treatments that can counter these symptoms and improve the lives of the hundreds of thousands of people living with the condition.’
She added: ‘Research has shown paracetamol could reduce agitation in people with dementia. However, this latest trial is looking at the memory in healthy adults, and it is therefore too early to suggest this could be the breakthrough we’ve been waiting for.’
The French team stress that patients should never self-medicate with paracetamol, as the research is still in the early stages, and may have side-effects.
Meanwhile, taking paracetamol long-term may lower the risk of prostate cancer.
New research by the Epidemiology Research Center at the American Cancer Society looked at the association between the painkiller and prostate cancer incidence among 80,000 men.
They had been monitored by scientists every two years since 1992 in an ongoing study. Since this date, a total of 8,092 prostate cancer cases were diagnosed.
Results show that for those using paracetamol — 30 or more pills a month — and who had done so for five or more years, the risk of prostate cancer was reduced by 48 per cent.
The risk of an aggressive cancer was reduced by 51 per cent.
The researchers are unsure how the painkiller delivers such a protective effect, but believe it may be linked to its anti-inflammatory properties.