In the March 1, 2008 issue of the AACR journal Cancer Research, Roswell Park Cancer Institute professor of oncology Yuesheng Zhang, MD, PhD and his colleagues report that an extract of broccoli sprouts given to rats reduced the development of bladder tumors by one half.
Dr Zhang’s team gave groups of rats a high or low dose of a concentrated extract of freeze dried broccoli sprouts two weeks prior to adding the carcinogen BBN to their drinking water. Other groups of animals received the broccoli sprout extract only, BBN only, or neither substance.
Bladder tumors did not develop in the group that received the broccoli sprout extract alone (without BBN), or who received neither treatment, however, among animals that received the carcinogen alone, 96 percent developed at least two tumors. Although 74 percent of BBN-treated rats that received the low dose of broccoli sprout extract developed cancerous tumors, only 38 percent of those that received the high dose developed any, and their tumors were much smaller in size and less numerous than those of the other groups.
The protective effect of broccoli and other cruciferous vegetables such as cabbage appears to be the result of their isothiocyanate (ITC) content. These phytochemicals have been associated with cancer protection in numerous other studies. Broccoli sprouts contain 30 times more ITCs than mature broccoli, and the compound used in the study provides 600 times more.
“Although this is an animal study, it provides potent evidence that eating vegetables is beneficial in bladder cancer prevention,” Dr Zhang stated. “The bladder is particularly responsive to this group of natural chemicals. In our experiments, the broccoli sprout ITCs after oral administration were selectively delivered to the bladder tissues through urinary excretion.”
“Epidemiologic studies have shown that dietary ITCs and cruciferous vegetable intake are inversely associated with bladder cancer risk in humans,” he added. “It is possible that ITC doses much lower than those given to the rats in this study may be adequate for bladder cancer prevention.”