Scientists have identified a vitamin that plays a key role in repairing damaged DNA and may lead to the development of a drug that can reverse ageing, fight cancer as well as help in space travel.

The study, published in the journal Science, identified how a vitamin called NAD+ -- naturally present in every cell of our body -- was regulating the interactions that control DNA repair.

Treating mice with a NAD+ precursor, or "booster", called NMN improved their cells' ability to repair DNA damage caused by radiation exposure or old age.

"The cells of the old mice were indistinguishable from the young mice, after just one week of treatment," said lead author David Sinclair, who is a professor at University of New South Wales in Australia

The findings may lead to drugs to treat cancer, Alzheimer's, protect astronauts from radiation during their various missions to space, as well as mitigate any effects of DNA damage for frequent flyers, the researchers said.

In addition, scientists have established that NAD+ could be useful for treating various diseases of ageing, female infertility and also treating side effects of chemotherapy.

Human trials of NMN therapy will begin within six months.

"This is the closest we are to a safe and effective anti-ageing drug that's perhaps only three to five years away from being on the market if the trials go well," Sinclair added.