WEDNESDAY, Jan. 22, 2020 (HealthDay News) -- Eating a diet high in vegetables and fruits does not slow or cure prostate cancer, according to a new study.

U.S. guidelines say prostate cancer patients might benefit from eating a vegetable-rich diet.

This study included 478 men, ages 50 to 80. All had been diagnosed with early-stage prostate cancer and were under active surveillance, meaning they were closely monitored and did not receive treatment unless their cancer started to progress.

The men were randomly assigned to either a control group that received written information about diet and prostate cancer or to a telephone counseling group in which they were encouraged to eat foods high in carotenoids. Those foods include leafy greens, carrots and tomatoes, and cruciferous vegetables such as broccoli and cabbage.

After two years of follow-up, the group on the vegetable-rich diet saw no extra protection against prostate cancer compared to the control group, according to findings published Jan. 14 in the Journal of the American Medical Association.

It's the first randomized clinical trial to assess the effects of diet changes on prostate cancer.

"These data indicate that, despite prevailing scientific and public opinion, eating more vegetables will not alter the course of prostate cancer. It will not, to the best of our knowledge, suppress or cure it," said lead investigator Dr. J. Kellogg Parsons, professor of urology at the University of California, San Diego School of Medicine.

"However, while eating a healthy diet rich in fruits and vegetables and getting more exercise may not cure cancer, it may keep the body stronger and healthier, which may help patients tolerate cancer treatments," he said in a university news release.

More information

The American Cancer Society has more on prostate cancer.