Aug. 25, 2000 -- Bad news for broccoli haters: researchers in North Carolina have found yet another reason why you should eat the dreaded vegetable.
Broccoli and certain other members of the cruciferous vegetable family -- including cabbage and bok choy -- appear to protect humans from lung cancer, according to the article, which was published in the Aug. 26th issue of the journal Lancet. The protection comes from chemicals known as isothiocyanates that are found in these vegetables.
"This paper is a major development," says John Weisburger, PhD, senior member of the American Health Foundation in Valhalla, N.Y. "We've known for years that people should eat their vegetables, but we now know why this is important."
The authors studied a group of about 18,000 men living in four small Chinese communities in Shanghai. They followed them for an 11-year period to see which of them developed lung cancer. The dietary intake of isothiocyanates in the cancer patients was compared to that of men who did not develop cancer.
The researchers found that the men with no detectable levels of isothiocyanates had a 36% greater chance of developing lung cancer than those who did have the chemical in their bodies. These results held true even after researchers took into account which subjects smoked and which did not.
"This lends weight to previous [research] showing that vegetable intake -- especially cruciferous vegetables -- is protective for lung cancer," lead author Stephanie London, MD, DrPH, tells WebMD. "And since this is the first data that has a specific marker for this [chemical] compound, it tends to give credence to the idea that it's this compound rather than other compounds in the vegetables" that has this effect. London is an epidemiologist at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C.
Although it isn't known just how these chemicals work, previous research has shown that isothiocyanates inactivate certain cancer-causing chemicals in tobacco smoke. The compounds may also work as antioxidants to help prevent natural damage to cells in the body.
"That's why we teach people they should eat five to 10 vegetables a day," says Weisburger, who notes that green tea and black tea may have the same effect.
The authors note that there are few studies on the link between isothiocyanates and cancer in humans, so their results should be considered preliminary. But, says Weisburger, "this study shows how these vegetables work and how they contribute to good health in general. It reinforces how important vegetables are."