A report in the March 1 issue of Cancer Research, a journal of the American Association for Cancer Research, describes how an extract of freeze-dried broccoli sprouts cut development of bladder tumors in an animal model by more than half.
This finding reinforces human epidemiologic studies that have suggested that eating cruciferous vegetables like broccoli is associated with reduced risk for bladder cancer. The study’s senior investigator, Yuesheng Zhang, MD, PhD, professor of oncology at Roswell Park Cancer Institute, says that although this is an animal study, "it provides potent evidence that eating vegetables is beneficial in bladder cancer prevention.”
There is strong evidence that the protective action of cruciferous vegetables derives at least in part from isothyiocyanates (ITCs), a group of phytochemicals with well-known cancer preventive activities.“The bladder is particularly responsive to this group of natural chemicals,” Zhang said. “In our experiments, the broccoli sprout ITCs after oral administration were selectively delivered to the bladder tissues through urinary excretion.”
Other cruciferous vegetables with ITCs include mature broccoli, cabbage, kale, collard greens and others. Broccoli sprouts have approximately 30 times more ITCs than mature broccoli, and the sprout extract used by the researchers contains approximately 600 times as much.
Zhang said humans at increased risk for this cancer likely do not need to eat huge amounts of broccoli sprouts in order to derive protective benefits.
“Epidemiologic studies have shown that dietary ITCs and cruciferous vegetable intake are inversely associated with bladder cancer risk in humans. It is possible that doses much lower than those given to the rats in this study may be adequate for bladder cancer prevention,” he said. In the group of animals given the broccoli extract, no tumors developed, and there was no toxicity from the extract shown in the rats, either.