Men who eat one or more servings of broccoli per week can reduce their risk of developing prostate cancer, a new British study says.

Researchers from the Institute of Food Research found that men who ate 400 g of broccoli per week over a 12-month period had significant changes in the actions of genes related to the development of cancer.

They also found that men who have prostate cancer can reduce the risk of their tumour becoming more aggressive by following the broccoli-rich diet.

The findings were published in the online journal PLoS One.

Researchers set out to document changes in the genes in the prostate gland before, during and after volunteers consumed either a broccoli-rich or pea-rich diet.

After six months, researchers found that prostate genes in men who consumed a broccoli-rich diet had more changes than genes in men on the pea-rich diet.

As well, the effect of the broccoli-rich diet was even more pronounced in the men who had a gene known as GSTM1. Previous studies have shown that people with this gene actually benefit more from eating broccoli than those who do not have this gene.

"This study provides, for the first time, experimental evidence obtained in humans to support observational studies that diets rich in cruciferous vegetables may reduce the risk of prostate cancer and other chronic disease," the authors wrote.

Prostate cancer is the most common non-skin cancer in men in western countries.

Lead study author, professor Richard Mithen, said that once scientists understand how different vegetables act on cell expression, "we can provide much better dietary advice in which specific combinations of fruit and vegetable are likely to be particularly beneficial."

Mithen said that the best advice for men for now is to eat two or three portions of cruciferous vegetables per week. In addition to broccoli, members of the cruciferous family include Brussels sprouts, cauliflower, cabbage, watercress, kale and radish.

Abstract:

Broccoli Consumption Interacts with GSTM1 to Perturb Oncogenic Signalling Pathways in the Prostate

Maria Traka, Amy V. Gasper, Antonietta Melchini , James R. Bacon, Paul W. Needs, Victoria Frost, Andrew Chantry, Alexandra M. E. Jones, Catharine A. Ortori, David A. Barrett, Richard Y. Ball, Robert D. Mills, Richard F. Mithen

Background: Epidemiological studies suggest that people who consume more than one portion of cruciferous vegetables per week are at lower risk of both the incidence of prostate cancer and of developing aggressive prostate cancer but there is little understanding of the underlying mechanisms. In this study, we quantify and interpret changes in global gene expression patterns in the human prostate gland before, during and after a 12 month broccoli-rich diet.

Methods and Findings: Volunteers were randomly assigned to either a broccoli-rich or a pea-rich diet. After six months there were no differences in gene expression between glutathione S-transferase mu 1 (GSTM1) positive and null individuals on the pea-rich diet but significant differences between GSTM1 genotypes on the broccoli-rich diet, associated with transforming growth factor beta 1 (TGFâ1) and epidermal growth factor (EGF) signalling pathways. Comparison of biopsies obtained pre and post intervention revealed more changes in gene expression occurred in individuals on a broccoli-rich diet than in those on a pea-rich diet. While there were changes in androgen signalling, regardless of diet, men on the broccoli diet had additional changes to mRNA processing, and TGFâ1, EGF and insulin signalling. We also provide evidence that sulforaphane (the isothiocyanate derived from 4-methylsuphinylbutyl glucosinolate that accumulates in broccoli) chemically interacts with TGFâ1, EGF and insulin peptides to form thioureas, and enhances TGFâ1/Smad-mediated transcription.

Conclusions: These findings suggest that consuming broccoli interacts with GSTM1 genotype to result in complex changes to signalling pathways associated with inflammation and carcinogenesis in the prostate. We propose that these changes may be mediated through the chemical interaction of isothiocyanates with signalling peptides in the plasma. This study provides, for the first time, experimental evidence obtained in humans to support observational studies that diets rich in cruciferous vegetables may reduce the risk of prostate cancer and other chronic disease.