The benefits of eating right and staying active may extend well beyond your physique, all the way down to your genes, Bay Area scientists have found.

Men with low-risk prostate cancer were able to change the activity of genes that affect tumor growth with diet and exercise, which could potentially reduce the risk of the cancer progressing.

"So often people say, 'It's all in my genes, what can I do?' Well, it turns out we can do a lot, and faster than we thought," said Dean Ornish of UC San Francisco, lead author of the study.

Turning certain genes on and off may not only help slow cancer progression, it could help prevent recurrence and perhaps prevent cancer from showing up in healthy people.

The team studied patients with low-risk prostate cancer because unlike patients with breast cancer or colon cancer, immediate chemotherapy or radiation isn't required, and the tumor can be safely monitored for growth.

"It may be that we can extrapolate beyond men with prostate cancer, to men in general and on to more people," Ornish said.

The scientists took prostate tissue from 31 men diagnosed with low-risk prostate cancer who chose not to undergo radiation or chemical treatment. Instead, the men followed a prescription for a low-fat, plant-based diet, an hour of daily stress management, a daily 30-minute walk, and group counseling. Ornish has detailed the regimen in his book, "The Spectrum."

After three months, the team took another tissue sample and found significant changes in the "expression," or activity, of several genes known to play a role in prostate cancer progression.

They found that more than 500 genes were beneficially affected. Genes that promote diseases such as breast and prostate cancers were less active while some disease-preventing genes had been turned on.

The results appear in the Proceedings of the National Academy of Sciences.

The findings could be particularly helpful for older patients whose prostate cancer shows up in a screening and could benefit from a less invasive intervention, such as lifestyle change, said biostatistician Ruth Etzioni of the Fred Hutchinson Cancer Research Center in Seattle.

"For old men, many may not die from their cancer. Some wouldn't have ever known if it hadn't been found in a screen," she said. "So, treating them for it is an extra treatment with side-effects and costs."

Ornish's study is the first of its kind, but other scientists are wading into the same area.

"Until now, the going view has been that if it's genetic, it's beyond our control," said cancer epidemiologist Gordon Saxe of the Moores Cancer Center at UC San Diego. "I see it more like the genes are kind of like the hardware and the diet and things we do are like the software."

Saxe is currently working on a similar study that will look at the effect of lifestyle and diet on about 20,000 genes.

"What we're probably going to find is that it's involved with the expression of a variety of genes in the body," he said.

Genes involved with cancer, heart disease, diabetes, depression, schizophrenia and other illnesses could all be affected, he said. "You name it, diet probably plays a role."

Ornish hopes his research will help generate funding for more studies that look at bigger groups of people for longer periods of time to find out if the gene alterations they saw after three months translate into better long-term outcomes.

Betsy Mason covers science and the national laboratories. Reach her at 925-952-5026 or bmason@bayareanewsgroup.com.