Years ago, scientists observed that eating vegetables, particularly the cruciferous ones that include broccoli, cabbage and bok choy, reduces the risk of lung cancer, the most common cause of cancer deaths in the U.S. among both men and women. Now, a study supported by NIH's National Institute of Environmental Health Sciences (NIEHS) and NCI gives a clearer, if somewhat complicated, picture of how these vegetables work their magic. Key to the findings is a group of molecules in the vegetables called isothiocyanates, along with two human genes called GSTM1 and GSTT1.

Isothiocyanates inhibit lung cancer in laboratory animals, but the connection had not yet been made in people. An NIEHS researcher collaborated with scientists at the American Health Foundation, the University of Southern California and the Shanghai Cancer Institute to look at 18,244 men in Shanghai, China, where isothiocyanate-rich vegetables are a major part of the diet. They looked at the eating and smoking habits of the men, who were between the ages of 45 and 64, between 1986 and 1989 and found 159 cases of lung cancer in follow-ups stretching to 1997. The scientists found that the men with detectable levels of isothiocyanates in their urine had a 36% lower risk of developing lung cancer.

The GSTM1 and GSTT1 genes code for enzymes that help eliminate cancer-causing compounds in cigarette smoke from the body. Men who were missing both of these genes and had no isothiocyanates in their urine had a higher risk of lung cancer. But these enzymes also help remove isothiocyanates from the body. The reduction in lung cancer risk associated with isothiocyanates in the urine turned out to be greatest in the men who were missing the GSTM1 and GSTT1 genes, presumably because the isothiocyanates were able to stay in the body longer.

Doubtless, there is a complex interplay between these genes and the isothiocyanates - and probably other, as yet unidentified, factors as well. However, this research provides the first direct evidence that isothiocyanates may help reduce the risk of lung cancer. Other research has found that eating broccoli, which is rich in isothiocyanates, can protect against colon polyps in people missing GSTM1, so this effect likely applies to more than just lung cancer. The benefits of eating vegetables may vary somewhat according to your genes, but one thing is certain: it can't hurt to eat your vegetables, and it could do a lot of good.

For more information about lung cancer, visit or call the Cancer Information Service (CIS) at 1-800-4-CANCER (1-800-422-6237) to speak with a Cancer Information Specialist.