"This is a rigorous and randomized study that provides valuable data which previously did not exist," said Moshe Shike, MD, lead author of the study and Director of the Memorial Sloan-Kettering Cancer Prevention Program. "Although this study found no protective effect over four years, it is possible that a healthy dietary pattern sustained over many more years will have an inhibitory effect on prostate cancer."
In the study, 1,350 men without prostate cancer were randomly assigned to the dietary intervention or a control group. The 689 men in the intervention arm received intensive nutrition counseling to consume a diet low in fat and high in fruits, vegetables and fiber, while the 661 men assigned to the control arm received a standard brochure detailing healthy dietary recommendations. To determine the change in PSA levels over time, researchers measured the PSA levels in both groups at the beginning of the study, and then annually for four years.
After four years, there was no marked difference in PSA levels between the two groups, and the proportion of patients with raised PSA levels was equal at each point over the four years. Incidence of prostate cancer during the study was also statistically similar between the two groups: 19 patients in the control arm and 22 in the intervention arm.
According to Dr. Shike, the intervention's failure to impact PSA levels should not be viewed as definitive evidence that diet has no preventive impact on prostate cancer. "The PSA is only a surrogate marker for prostate cancer, and it is possible that diet could impact the occurrence and growth of prostate cancer without drastically affecting PSA levels." The study had too few participants and was too short to determine the impact of diet on the actual incidence of prostate cancer.
According to researchers, limiting calories and eating a fruit- and vegetable-enriched low-fat diet – with fat intake making up 20-25 percent of a person's daily intake of calories – should continue to be upheld as part of a healthy lifestyle.
"Lack of Effect of a Low-Fat, High-Fruit, -Vegetable, and -Fiber Diet on Serum Prostate Specific Antigen of Men Without Prostate Cancer: Results From a Randomized Trial." Moshe Shike, M.D., et al.; Memorial Sloan-Kettering Cancer Center, New York, NY. Vol 20, No 17 (September 1) 2002, pp: 3592-3598.
The Journal of Clinical Oncology is the semi-monthly peer-reviewed journal of the American Society of Clinical Oncology (ASCO), the world's leading professional society representing physicians who treat people with cancer.
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