The latest research says that by eating just three servings a month of raw broccoli or cabbage a person can reduce their risk of bladder cancer by as much as 40 percent.
The researchers from the Roswell Park Cancer Institute in Buffalo, New York, reached this conclusion after conducting a survey of over 1,000 people where the participants were asked specifically about their intake of cruciferous vegetables.
The researchers were particularly interested in vegetables such as broccoli and cabbage which are rich in compounds called isothiocyanates and are known to lower the cancer risk.
Of the participants 275 people had been diagnosed with bladder cancer and 825 were healthy.
They were asked about pre-diagnosis intakes of raw and cooked vegetables, their cigarette smoking habits, and other risk factors.
The researchers found that the effects were most significant in nonsmokers who ate at least three servings a month and were about 73% less likely to develop bladder cancer than those who smoked and ate less than three servings a month.
Among both smokers and nonsmokers, those who ate this minimal amount of raw veggies had a 40 percent lower risk, but the team did not find the same effect for cooked vegetables.
Dr. Li Tang, who led the study, says cooking can reduce by 60 to 90 percent the isothiocyanates (ITCs) in foods.
ITCs are found in broccoli, cauliflower, kale, turnips, collards, Brussels sprouts, cabbage, radish, turnip and watercress.
When the vegetables are eaten raw isothiocyanates are released which have been shown to neutralise carcinogens and stimulate their secretion.
Studies have shown that isothiocyanates help to prevent lung cancer and esophageal cancer and also lower the risk of other cancers, including gastrointestinal cancer.
The researchers tested the theory using broccoli sprouts in rats who had been engineered to develop bladder cancer.
The rodents were fed a freeze-dried extract of broccoli sprouts and it was found that the more they ate, the less likely they were to develop bladder cancer.
The researchers say the compounds were processed and excreted within 12 hours of feeding which suggests that the compounds are protecting the bladder from the inside.
Lead researcher Dr. Yuesheng Zhang says the bladder is like a storage bag, and cancers in the bladder occur almost entirely along the inner surface, the epithelium, that faces the urine, presumably because this tissue is assaulted all the time by noxious materials in the urine.