BUFFALO, N.Y. — For years now, national guidelines have recommended men with prostate cancer should eat a plant-based diet to possibly decrease cancer progression and lower their chance of death. 

A new study, led by researchers at Roswell Park and the University of California, San Diego, shows that eating more produce won't cure nor stop the disease. 

The study, which will be published in the Journal of the American Medical Association, looked at nearly 500 American men between the ages of 50 and 80 who had been diagnosed with early stages of prostate cancer. 

Patients were either assigned to a control group where they received written information about prostate cancer and their diet or to a phone counseling behavioral intervention program, which encouraged them to eat foods that are high in carotenoids. 

Previous studies suggest that foods with high carotenoids have antioxidant properties, which can protect men from prostate cancer. Some of those foods include leafy greens, broccoli, cabbage, carrots, and tomatoes. 

All of them were monitored for two years. 

“Patients assigned to the intervention increased their intake of fruits and vegetables to a statistically significant degree, and significantly more than control patients did," said James Marshall, PhD from Roswell Park. "These findings were supported by significant changes in the blood carotenoid levels of patients. Nonetheless, these data fail to support prevailing assertions in clinical guidelines and the popular media that diets high in micronutrient-rich vegetables improve cancer-specific outcomes among prostate cancer survivors.”

Researchers say the impact of nutrition on diseases is an ongoing conversation among researchers and doctors.

Click here to read the full study.

RELATED: Cancer group finds biggest one-year drop in U.S. death rate

RELATED: New drugs show rare promise against aggressive breast cancer

RELATED: Roswell Park makes strides in fight against prostate cancer