February 5, 2000: Several studies in the January 2000 issue of the Journal of Urology (www.jurology.com) provide more evidence that high-fibre diets, especially those high in soluble fibre, can reduce the risk of prostate cancer.
Researchers with the Proscar Long-Term Efficacy and Safety (PLESS) study followed placebo-treated men with benign prostate hyperplasia (BPH), and found a strong correlation between baseline PSA (prostate specific antigen) and amount of future prostate growth. This suggests that elevated serum PSA is a significant risk factor for BPH, which often leads to acute urinary retention and the need for prostate surgery in aging men.
University of Toronto researchers found that healthy men consuming 60 to 90 grams of soluble fibre (i.e., oat bran and legumes) per day had slightly lower levels of PSA in their blood than men consuming similar amounts of insoluble fibre (i.e., wheat bran). This small but statistically significant difference was attributed to increased excretion of certain bile acids.
Prostate cancer is a hormone-dependent cancer in which tumour growth is stimulated by sex hormones. Although soluble fibre was strongly correlated with decreased serum PSA in the Toronto study, the link could not be attributed to decreased circulating testosterone levels. Further investigation is needed to determine the mechanism and potential clinical value of the relationship between soluble fibre and PSA.
Although the importance of these results for the prevention of prostate cancer is yet to be determined, it is one more reason to include more vegetables and legumes in our diets.