A naturally occuring substance that can create "immortal cells" could be the key to finding a real elixir of youth, scientists claim. Researchers believe boosting the amount of a naturally forming enzyme in the body could prevent cells dying and so lead to extended, healthier, lifespans.

The protein telomerase helps maintain the protective caps at the ends of chromosomes which act like the ends of shoelaces and stop them unravelling. As we age, and our cells divide, these caps become frayed and shorter and eventually are so damaged that the cell dies. Scientists believe boosting our natural levels of telomerase could rejuvenate them.

A team at the Spanish National Cancer Centre in Madrid tested the theory on mice and found that those genetically engineered to produce 10 times the normal levels of telomerase lived 50 per cent longer than normal.

Maria Blasco, who led the research, told the New Scientist said that the enzyme was capable of turning "a normal, mortal cell into an immortal cell". She adde