Remember when your mom insisted that you eat broccoli? Well, scientists say they've proved that mother knows best.
Dr. Paul Talalay of Johns Hopkins University School of Medicine said in a paper published Sunday that studies in his lab show broccoli is rich in sulforaphane, a chemical that works as a powerful anti-cancer compound in laboratory mice.A number of earlier studies have shown that a diet rich in cruciferous vegetables such as a broccoli, Brussels sprouts, cabbage and cauliflower, can lower the risk for cancer of the bowel, stomach and breast. But just how those vegetables caused the effect wasn't clear.
Now, Talalay said, it appears that at least one anti-cancer ingredient in the vegetables is sulforaphane, and that it works by causing cells to expel cancer-causing toxins.
"This is the first time a compound of such high potency has been isolated from vegetables and has been shown to accelerate the detoxification process" in cells, he said.
Talalay said his team isolated sulforaphane from broccoli, then fed it to a group of mice. When cells in the mice were examined after five days, the scientists found that the chemical had triggered enzymes known to neutralize carcinogens within cells.
Research, Talalay said, will shift to the long-term cancer-fighting effects of the chemical. However, he said, "our prediction is that sulforaphane will block tumor formation in animals and presumably in man."
The studies are part of a continuing effort by nutrition and medical scientists to find ways to prevent cancer through a diet rich in foods that have anti-tumor properties and lacking in foods that might nurture cancer.
"We're interested in chemo-protection against cancer," Talalay said. "This I define as establishment of a state of reduced susceptibility to chemical carcinogens."
In earlier studies, Talalay said he and others have shown that certain proteins in cells, called Phase I enzymes, can take innocent chemicals and turn them into carcinogens, or compounds that can give rise to cancer by disrupting the genetic pattern in cells.
Other proteins, called Phase II enzymes, he said, tend to block formation of carcinogens, or facilitate their excretion.
Sulforaphane, he said, is a potent activator of Phase II enzymes.
"There is mounting evidence that if you are able to raise the Phase II enzymes, this will divert the carcinogenic compounds from damaging the (genes)," Talalay said. "By tilting this balance toward Phase II enzymes, we can achieve protection from cancer."
Talalay said his team found that other vegetable foods, ranging from bok choi and green onions to ginger, contained significant amounts of sulforaphane. But he said they decided to concentrate on broccoli because it was a popular vegetable.