PURPOSE:Epidemiological and laboratory evidence indicates that a Western diet is associated with an increased incidence of prostate cancer. Specific components of the diet, such as high saturated fat, low fiber and high meat content, may have greatest clinical significance in the later stages of tumor promotion and progression. However, departure from the conventional diet is difficult to initiate and maintain. Therefore, we combined the well-known Mindfulness-Based Stress Reduction (MBSR) program with a low saturated fat, high-fiber, plant-based diet to determine the effect on the rate of change in prostate specific antigen (PSA) in patients with biochemical recurrence after prostatectomy. MATERIALS AND METHODS: We enrolled 10 men and their partners in a 4-month group-based diet and MBSR intervention. A pre-study post-study design in which each subject served as his own control was used to compare the rate of increase in and doubling time of PSA before and after intervention. RESULTS: The rate of PSA increase decreased in 8 of 10 men, while 3 had a decrease in absolute PSA. Results of the signed rank test indicated a significant decrease in the rate of increase in the intervention period (p = 0.01). Estimated median doubling time increased from 6.5 months (95% confidence interval 3.7 to 10.1) before to 17.7 months (95% confidence interval 7.8 to infinity) after the intervention. CONCLUSIONS: Our small study provides evidence that a plant-based diet delivered in the context of MBSR decreases the rate of PSA increase and may slow the rate of tumor progression in cases of biochemically recurrent prostate cancer. Larger-scale randomized studies are warranted to explore further the preventive and therapeutic potential of diet and lifestyle modification in men with prostate cancer.