Broccoli, other cruciferous vegetables may help prevent bladder cancer

December 20, 2007

Researchers at Roswell Park Cancer Institute in Buffalo, NY, have found that broccoli sprouts, a rich source of isothiocyanates, may play a direct role in preventing bladder cancer.

Researchers at Roswell Park Cancer Institute in Buffalo, NY, have found that broccoli sprouts, a rich source of isothiocyanates, may play a direct role in preventing bladder cancer.

“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,” said senior author Yuesheng Zhang, MD, PhD. “The isothiocyanates in broccoli sprout extracts after oral ingestion are selectively delivered to the bladder epithelium through urine excretion.”

Using a rat model of bladder cancer, Dr. Zhang and his colleagues found that freeze-dried aqueous extract of broccoli sprouts significantly and dose-dependently inhibited bladder cancer development. The incidence, multiplicity, size, and progression of bladder cancer all were inhibited by the extract, while the extract itself caused no observable changes in the bladder. This protective effect of the extract was associated with a significant increase in the bladder of several enzymes that are known to protect against oxidants and carcinogens, the researchers reported at an American Association for Cancer Research conference on cancer prevention in Philadelphia.

In a separate study from the same institution, researchers report that three or more servings per month of raw cruciferous vegetables, such as broccoli, cabbage, and cauliflower, may reduce bladder cancer risk by approximately 40%.

They surveyed the dietary habits of 275 individuals with incident, primary bladder cancer and 825 individuals without cancer and surveyed them about their pre-diagnostic intake of raw and cooked cruciferous vegetables, smoking habits, and other cancer risk factors. They observed a strong and statistically significant inverse association between bladder cancer risk and raw cruciferous vegetable consumption. When compared with smokers who ate fewer than three servings of raw vegetables per month, non-smokers who ate at least three servings per month were almost 73% less likely to develop bladder cancer, the researchers found.

“Cooking can reduce 60% to 90% of isothiocyanates,” said Li Tang, MD, PhD, lead researcher. “Heating destroys the enzyme that converts the precursor glucosinolates into isothiocyanates and also destroys isothiocyanates already formed, which is why you need to eat raw cruciferous vegetables to receive the food’s maximum benefit.”