Scientists have discovered how the ageing process is controlled in yeast - and hope it will help them find ways to turn back the clock in humans.

Researchers know that ageing can be slowed by reducing the number of calories taken in to the body.

There is evidence that a reduced calorific intake can slow down both the deterioration of the body, and the march of age-related diseases.

We believe that these studies could lead to the development of a drug

Dr Leonard Guarente, Massachusetts Institute of Technology

However, it would be very difficult to follow a diet that could achieve this effect.

The new discovery raises the possibility of developing drugs that could do the same thing without the need for a brutally strict diet.

Researchers from the Massachusetts Institute of Technology (MIT) have discovered a gene, SIR2, that appears to control how nutrition impacts on the ageing process in yeast spores.

The gene is responsible for the production of a protein, Sir2.

The higher the level of this protein, the longer the life span of yeast cells.

The researchers believe that Sir2 acts in combination with another - as yet unknown - compound to slow the ageing process.

Drug development

MIT researcher Dr Leonard Guarente said: "Our findings thus provide a model for ageing that is universal and explains how calorie restriction extends life span.

"We believe that these studies could lead to the development of a drug that intervenes to strengthen the Sir2-silencing process and provides the benefits of calorie restriction without the extreme difficulty of the regimen itself."

In separate research, a team from Louisiana State University has shown that manipulating the nutritional intake of yeast cells can increase their life span.

Not only did calorific restriction extend the life-span of these cells, it also postponed many of the physical manifestations of ageing.

Lead researcher Dr Michal Jazwinski said: "If we could elucidate these mechanisms, it is likely that we would be able to develop relatively simple interventions that would alleviate the ravages of the ageing process and improve quality of life in the later years in humans."

The research was reported at a meeting of the American Society for Microbiology.