A team led by experts at the US National Cancer Institute in Maryland tracked 29,000 men over a four-year period.

All the men were regularly screened for signs of prostate cancer, and researchers also monitored their diets.

There were far fewer cases of fast-growing tumours, which are likely to spread through the body, in those who ate cauliflower or broccoli at least once a week.

But vegetable and fruit consumption was not related to prostate cancer risk overall,  according to the study published yesterday in the Journal of the National Cancer Institute.

Some prostate tumours are slow-growing and rarely spread to other organs, while others are much more aggressive and have a poor survival rate.

The study concluded that a high intake of cruciferous vegetables, including broccoli and cauliflower, may be associated with reduced risk of aggressive prostate cancer, particularly extraprostatic disease.

The risks of contracting prostate cancer increase with age. Men over 50 are more likely to develop a tumour, and there is a strong genetic element to it.

One of the first signs can be frequent urination, as the tumour presses on the urethra – the tube that carries urine out of the body.

Cancer charities last night welcomed the report’s findings, though they recommended a good intake of several types of fruit and vegetables within a healthy, balanced diet to help protect against the disease.

Chris Hiley, The Prostate Cancer Charity’s head of policy and research, said: “This is yet another study that shows men should be eating up their vegetables.

“Broccoli and cauliflower have appeared in other studies as being potentially important in defences against prostate cancer.

“In the meantime, whilst waiting for definitive evidence, it’s clear that men should be eating at least five portions of fruit and vegetables a day. Hopefully they’ll be enjoying them too.”

Dr Kat Arney, Cancer Research UK’s science information officer, said: “When it comes to food, there is no one particular “super” fruit or vegetable that will protect you from cancer.

“Experts have proven that the best way to reduce your risk of many cancers is to eat a healthy balanced diet.

“This should include at least five portions a day of a variety of fruit and vegetables including broccoli and cauliflower.”
Prostate cancer claimed the life of comedian Bob Monk-house four years ago at the age of 75, and kills 10,000 men a year in the UK.

Earlier this year the Daily Express reported how eating broccoli and tomato together was claimed to help fight prostate cancer.

Researchers from the University of Illinois, writing in journal Cancer Research, estimated that one-and-a-half cups of broccoli and two-and-a-half cups of tomatoes daily was the ideal amount.

Researcher Kirstie Canene-Adams said sufferers “should seriously consider altering their diets”.

Health-conscious Britons have sent sales of superfoods soaring. The potential health benefits of such foods include the ability to ward off cancers, banish cellulite and wrinkles and even boost sex drive.

Many superfoods are rich sources of vitamins A, C and E as well as several antioxidants.

Last year, a report published in the British Journal of Cancer found that naturally occurring chemicals found in certain vegetables, like broccoli, cauliflower and cabbage, can enhance DNA repair in cells, perhaps helping to stop them becoming cancerous.