British scientists at the Institute of Food Research have found that men who ate one daily portion of broccoli had altered patterns of gene activity in their prostates, compared with men who ate a 'control' diet of a daily portion of peas.
The effect was more pronounced among men who carried a gene called GSTM1 - which is thought to be involved in the processing of the suspected 'active ingredient' of broccoli, and is carried by half the UK population.
The finding adds to several lines of evidence that the chemicals in broccoli might be able to reduce prostate cancer risk.
While this is important research, it was only based on a small number of men. Our best advice is to eat a healthy balanced diet that is high in all types of fruit and vegetables.
- Dr Jodie Moffat, health information officer, Cancer Research UK
But the study didn't look at whether the men actually went on to develop cancer.
A team led by Professor Richard Mithen recruited men who were asked to eat either 400g of broccoli or 400g of peas every week for 12 months, in addition to their regular diet.
All of the 22 volunteers in the study had been diagnosed with 'high-grade prostatic intraepithelial neoplasia' - a pre-cancerous condition of the prostate gland.
Scientists took tissue samples from the men's prostate before the trial, and again after six and 12 months - and analysed the activity of key genes in each one.
They found that tissue taken from men who ate broccoli had more changes in the activity of several genes known to be involved in controlling cell multiplication and growth - than tissue taken from men who ate peas.
The findings are published in the journal PLoS One and the researchers are now planning further studies.
Dr Jodie Moffat, health information officer at Cancer Research UK, commented: "Our understanding of how diet may affect cancer risk is rapidly growing but it is still very incomplete.
"Broccoli has had a lot of research focussed on it due to some of the chemicals in the vegetable. While this is important research, it was only based on a small number of men and the effect wasn't seen in all of them.
"So, our best advice is to eat a healthy balanced diet that is high in all types of fruit and vegetables."
Stomach bacteria may prevent some oesophageal cancers
"Research needed" to develop breast cancer prevention drug
India bans smoking in public places
Vitamin C may reduce effectiveness of anti-cancer drugs
Black men face higher prostate cancer risk
Tobacco products to carry stark picture warnings
Low-cost test for hereditary breast cancer could soon be available
Study uncovers commercial links between early Hollywood and tobacco firms
Cancer drug availability varies widely across the UK
Cancer patients to get free prescriptions