A concentrated extract of freeze-dried broccoli sprouts
tumor 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 and other cruciferous
vegetables is associated with a lower risk of bladder
"Although this is an animal study, it provides potent
evidence that eating vegetables is beneficial in bladder
cancer prevention," senior investigator Dr. Yuesheng
Zhang, a professor of oncology at Roswell
Park Cancer Institute, said in a prepared statement.
It's believed that the protective effect of broccoli
and other cruciferous vegetables -- such as cabbage, kale,
and collard greens -- is at least partly due to isothyiocyanates
(ITCs), a group of phytochemicals with anti-cancer properties.
"The bladder is particularly responsive to this
group of natural chemicals," Zhang said.
He and his colleagues 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 tumors developed in 96 percent
of the rats that didn't receive the extract, compared
to an average of 1.39 tumors in 74 percent of the rats
that received a low dose of the extract, and an average
of .46 tumors in 38 percent of the rats that received
a high dose of the extract.
The findings were published in the March 1 issue of the
journal Cancer Research.
Broccoli sprouts have about 30 times more ITCs than mature
broccoli, and the sprout extract used in this study has
about 600 times as much. But Zhang said humans at risk
for bladder cancer likely wouldn't have to eat large
amounts of broccoli sprouts to achieve protective effects.
"Epidemiologic studies have shown that dietary ITCs
and cruciferous vegetable intake are inversely associated
cancer risk in humans. It is possible that ITC
doses much lower than those given to the rats in this
study may be adequate for bladder cancer prevention,"