A concentrated extract of freeze-dried broccoli sprouts reduced bladder tumour development by more than half in laboratory rats, according to a new study. Researchers said the finding supports human epidemiologic studies, indicating that eating broccoli is associated with a lower risk of bladder cancer.

Senior investigator Dr. Yuesheng Zhang, of Roswell Park Cancer Institute in Conyers, Georgia, said: “Although this is an animal study, it provides potent evidence that eating vegetables is beneficial in bladder cancer prevention.”

It is believed that the protective effect of broccoli and other vegetables, such as cabbage, kale, and collard greens, is at least partly due to isothyiocyanates, a group of phytochemicals with anti-cancer properties.

Researchers tested the freeze-dried broccoli sprout extract in rats given a chemical that induces bladder cancer. One group of rats did not receive the extract, while two other groups of rats were given either a low or high dose of the extract in their food, beginning two weeks before they received the cancer-causing chemical.

An average of about two tumours developed in 96 per cent of the rats that did not receive the extract, compared with an average of 1.39 tumours in 74 per cent of the rats that received a low dose of the extract, and an average of 0.46 tumours in 38 per cent of the rats that received a high dose of the extract.