Red wine could help us live longer, scientists have claimed – reviving a furious debate over an ingredient once dubbed the ‘elixir of youth’.

Resveratrol, which protects red grapes, cacao beans and Japanese knotweed against infections and drought, has divided experts for a decade over reports it could make humans live longer.

Now a study claims it could prolong our lives after all, because it imitates another protective enzyme – and just a ‘couple of glasses’ of red wine may be enough to benefit.

The study, published in the journal Nature, claimed it was time to finally ‘dispel much of the mystery and controversy about how resveratrol really works’.

Tests on mice previously showed resveratrol increased their lifespan and stamina and prevented diabetes, but critics complained it was being used in ‘unrealistically high doses’.

So the new study’s authors used a much weaker dose, up to 1000 times smaller than before.

Their breakthrough then came when they combined resveratrol with an enzyme called TyrRS, which binds to the nucleus of a cell when it is under stress.

They found that when resveratrol and TyrRS were combined – as can happen naturally in the body – the pair imitate a cell-healing amino acid called tyrosine.

That process in turn activated a protein called PARP-1 which has a ‘DNA-repair factor thought to have a significant influence on lifespan’, the researchers said.

Dr Mathew Sajish of the California-based Scripps Research Institute, who led the study, said: ‘Based on these results, it is conceivable that moderate consumption of a couple of glasses of red wine would give a person enough resveratrol to evoke a protective effect via this pathway.

‘With these findings we have a new, fundamental mechanism for the known beneficial effects of resveratrol.’

The pair said they came to the controversy over resveratrol as ‘outsiders’, because they had been better known for their work on enzymes such as TyrRS.

Their interest was sparked when a colleague found ‘hints’ that TyrRS could move to the nucleus of a cell and take on an ancient protective role.

To test the theory, they injected mice with their combination of resveratrol and TyrRS.

They found it triggered a ‘stress response’, activating host of genes which lengthened the mice’s lives – including the tumor-suppressor gene p53 and the longevity genes FOXO3A and SIRT6.

Study author Paul Schimmel said: ‘This stress response represents a layer of biology that has been largely overlooked.

‘Resveratrol turns out to activate it at much lower concentrations than those used in prior studies.

The study said: ‘Why would resveratrol, a protein produced in plants, be so potent and specific in activating a major stress response pathway in human cells?

‘Probably because it does much the same in plant cells, and probably again via TyrRS – a protein so fundamental to life, due to its linkage to an amino acid, that it hasn’t changed much in the hundreds of millions of years since plants and animals went their separate evolutionary ways.’

Mr Schimmel added: ‘We think this is just the tip of the iceberg.

‘We think there are a lot more amino-acid mimics out there that can have beneficial effects like this in people, and we’re working on that now.’

It’s not all good news for red wine lovers, however.

The researchers shied away from saying exactly how often a ‘couple of glasses’ might be healthy – so don’t draw up a drinking diary yet.