Men who had been treated with surgery or radiotherapy for the disease were given a capsule containing essence of pomegranate, green tea, turmeric and broccoli.
At the end of a six-month trial, their PSA levels - a protein which is an indicator of the cancer - were 63 per cent lower than those who took a placebo.
While lab tests and small non-randomised studies have previously suggested that such foods, which are rich in polyphenol, have an anti-cancer effect, the British study is the first to demonstrate such an impact on sufferers of prostate cancer, compared with those who were not given the capsules.
Prof Robert Thomas, a consultant oncologist at Bedford Hospital and Addenbrooke’s Hospital in Cambridge will present the results of the “Pomi-T” study at the American Society of Clinical Ontology in Chicago today.
Diets rich in polyphenols, the natural plant-based phytochemicals found in healthy foods, have been linked with lower risks of chronic illnesses such as dementia, high cholesterol, arthritis, heart disease, skin aging and macular degeneration.
Studies have also linked their regular intake with lower risks of many cancers including breast, pancreatic, oesophageal, ovarian, prostate, and skin cancer.
Research has also found that breast cancer survivors eating polyphenol-rich fruit, vegetables, soy and green tea were found to have lower relapse rates.
The anti-cancer effect of polyphenols works because of their anti-oxidant properties, which protect the DNA from oxidative damage from carcinogens. The substances also work by killing cancer cells and inhibiting their proliferation.
Professor Thomas said: “Our experience in offering high-quality clinical care, collaboration with cancer charities and world-class research with the University of Cambridge has resulted in findings which will have an world-wide impact.
"We hope this will help millions of men to help combat the onset of prostate cancer.
The study found virtually no adverse affects among the group who were given the supplement.
Because of the lowered PSA levels among those given the capsule significantly fewer men proceeded to potentially toxic therapies at the end of the study, the study said.
“Healthy eating and lifestyle is the main way of helping to combat the development of cancer but men can now also turn to a whole food supplement which has been shown to work,” said Prof Thomas.