American researchers may have found the fountain of youth. But it will take major lifestyle changes for the average person to get there.

A radical diet and exercise plan, which includes following a vegan diet and exercising nearly every day, increases the levels of a protein that may delay aging and increase life expectancy, the new research suggests.

These and other diet and exercise changes increase an enzyme called telomerase, which helps protect cells from age-related damage.

The findings are published in the journal Lancet Oncology.

Telomerase helps repair and strengthen the caps, called telomeres, that are found at the end of chromosomes and protect cells from aging.

Telomeres protect the ends of chromosomes, which carry DNA, to keep them stable. As telomeres weaken and get shorter, cells age and die more rapidly - the shorter the telomeres, the shorter the life.

Shorter telomeres have become an indicator of disease risk and premature death in those suffering from many types of cancer, such as breast, prostate, colorectal and lung.

Professor Dean Ornish of the Preventive Medicine Research Institute in California, along with colleagues from the University of California San Francisco, studied 24 men who had prostate cancer.

The subjects followed a strict lifestyle regimen that included:

• a diet rich in whole foods, fruits and vegetables and low in refined sugar
• getting only 10 per cent of calories from fat
• fish oil and vitamin supplements
• one hour of meditation or relaxation per day
• 30 minutes of exercise six days per week

After three months, the researchers found that the study subjects' telomerase levels increased by 29 per cent.

An increase in telomerase was also linked with a decrease in LDL, or so-called "bad" cholesterol, as well as decreased stress levels.

"The implications of this study are not limited to men with prostate cancer," the authors conclude in their study. "Comprehensive lifestyle changes may cause improvements in telomerase and telomeres that may be beneficial to the general population as well."

Long-term research still needs to be done to confirm that an increase in telomerase will lead to greater longevity, the authors said.

The fact that the lifestyle changes led to an increase in a protective enzyme is a positive first step to determine if it's possible to slow down the aging process.