WASHINGTON (Reuters) – Broccoli and similar vegetables appear to offer special protection from cancer for smokers, researchers reported this week.

They found that former smokers and, especially, people still smoking heavily got special benefits from eating the vegetables.

"The most significant effect was in heavy smokers," Li Tang of Roswell Park Cancer Institute in Buffalo, New York, who led the study, said in a telephone interview. People who smoked more than 20 cigarettes a day were considered heavy smokers.

Broccoli and other so-called cruciferous vegetables such as cabbage, cauliflower and Brussels sprouts have been known to lower the risk of cancer in general, perhaps through compounds called isothiocyanates.

Tang and colleagues studied 948 cancer patients and 1,743 people being screened for cancer who turned out not to have it. All answered detailed questionnaires about habits, including their diet and smoking history.

People who ate cruciferous vegetables, especially raw, were between 20 percent and 55 percent less likely to have cancer than those who did not or only rarely ate these foods, Tang told a meeting of the American Association for Cancer Research.

The reduction in risk depended on the type of vegetable consumed and the duration and intensity of smoking.