University of Toronto researchers have discovered more evidence that high-fibre diets, specifically those high in soluble fibre such as oat bran and legumes, protect against prostate cancer. In a study published in a recent issue of the Journal of Urology, the researchers found that men on a diet high in soluble fibre for four months had lower levels of prostate specific antigen (PSA) - an indicator of prostate cancer risk - in their blood than men on high insoluble fibre diets. Insoluble fibre is contained in foods such as wheat bran cereal and breads.
"Prostate cancer is a hormone-dependent cancer, which means it may be modified if there is a reduction in the male sex hormones that stimulate tumour growth," says lead author Professor David Jenkins of the department of nutritional sciences. "The hormones, which are produced from cholesterol, circulate through the body and a proportion of these steroids are excreted through the digestive process.
Soluble fibre increases the output of steroids in the feces and we hypothesized that it would also result in a greater loss of hormones, which would reduce the stimulation of the prostate and therefore lower the PSA level.
Although we found greater fecal losses of total steroids, the hoped-for reduction in circulating hormone levels was not observed. Thus our overall hypothesis that soluble fibre may have an effect appears to be correct though we do not have an exact indication of the mechanism yet."
Prostate cancer is the most frequently diagnosed cancer in Canadian men, with one in eight expected to suffer from the disease in his lifetime, according to the Canadian Cancer Society. "Though it remains to be seen whether over the course of a lifetime this dietary factor makes an important difference, these results go along with existing advice to eat more vegetable foods and less animal products in the prevention of prostate cancer," Jenkins says. "It is further reinforcing what has been general advice about fibre, but perhaps gives another reason for taking it."
