Broccoli appears to lower the risk of lung cancer in smokers and ex-smokers, according to a new study.

Li Tang of the roswell Park Cancer Institute said that cruciferous vegetables don't eliminate the threat of cancer, but they help.

"Broccoli is not a therapeutic drug, but for smokers who believe they cannot quit nor do anything about their risk, this is something positive," Tang said. "People who quit smoking will definitely benefit more from intake of cruciferous vegetables."

Other common cruciferous vegetables include kale, collard greens, cabbage, brussels sprouts, cauliflower and bok choi.

A team studied lung-cancer patients and people without it who had similar diets and smoking habits. It included all commonly consumed cruciferous vegetables, as well as whether they were eaten raw or cooked.

Among smokers, the protective effect of cruciferous vegetable intake ranged from a 20 percent reduction in risk to a 55 percent reduction, depending on the type of vegetable consumed and the duration and intensity of smoking, according to a news release.

Also, raw vegetables were the only kind found to offer protection to current smokers.

"These findings are not strong enough to make a public health recommendation yet," said Li. "However, strong biological evidence supports this observation. These findings, along with others, indicate cruciferous vegetables may play a more important role in cancer prevention among people exposed to cigarette-smoking."