A strict vegetarian diet combined with relaxation therapy and exercise may be able to control slow-growing prostate cancer, researchers said on Thursday.
Diet guru Dr. Dean Ornish said his vegan diet program, which some studies have suggested can reverse heart disease, also seemed to halt the progression of prostate cancer.
Tests on middle-aged and elderly men who had opted to watch indolent prostate tumors rather than treat them suggested the program slowed the growth of their cancers, Ornish said.
"This is not the definitive study, but it certainly advances the field and it adds new information about how powerful these simple changes can be," Ornish said in a telephone interview.
Writing in the Journal of Urology, Ornish and colleagues at the University of California San Francisco and the Memorial Sloan-Kettering Cancer Center in New York said they tested 93 men with prostate cancer.
They had an average age of 65 to 67.
Prostate cancer is diagnosed in more than 200,000 men every year in the United States and will kill 29,000 this year, according to the American Cancer Society.
It can sometimes be a slow-growing cancer and men often opt for "watchful waiting" when they have been diagnosed. They get regular tests of prostate specific antigen, or PSA - a compound in the blood that can help indicate prostate health - digital rectal exams and sometimes ultrasounds of the prostate, reports Reuters.
According to CNN, other cellular tests suggested the diet wasn't just affecting PSA production, Ornish said.
"It's hard to get too excited about these results because you took a population of men who, frankly, are likely to do well no matter what," cautioned Dr. Durado Brooks of the American Cancer Society. But, "this definitely should open the door to more research."
"This report undoubtedly will excite the aficionados and devotees of lifestyle changes for cancer but it should also give pause to the skeptics," wrote Dr. Paul Lange of the University of Washington in an accompanying editorial.
Indeed, it comes just months after another study suggested low-fat diets might help women avoid a recurrence of breast cancer.
Ornish stressed that his study, partly government-funded, doesn't mean men should opt for diet over conventional therapy.
But these men weren't getting conventional treatment anyway, allowing a clearer test of dietary effects, he explained. The diet may help men undergoing therapy, too, he added.