Current smokers who ate three servings or less of salad a week were two times more likely to develop lung cancer than current smokers who ate four or more salads a week. Current smokers who gardened were 33 percent less likely to get lung cancer than current smokers who didn't garden, the Texas team found.

"Although this is a very preliminary analysis, it give us some important clues about how everyone -- smokers and non-smokers alike -- might be able to reduce their risk of developing lung cancer," Michele Forman, a professor of epidemiology at the University of Texas, said in a prepared statement.

"If you are worried about lung cancer risk, this study shows that you may benefit from eating a healthy diet and being physically active," she said.

A second study suggests that males may be more prone to developing cancer than females because of gender differences in antioxidant levels and the ability to repair DNA damage.

The Ohio State University study found that the same degree of damaging ultraviolet (UV) light caused more damage to the skin of male mice than to that of female mice. As a result, the male mice developed more squamous cell skin cancers, and these tumors grew more quickly and aggressively than the same type of tumors on the skin of female mice.

The findings may help explain why men develop three times as many squamous cell skin cancers than women and why men are more prone to developing cancer in general, the researchers said.

"Men get more skin cancer than women, and it has classically been thought that the reason for this is lifestyle -- men spend more time outside and are less likely to use sun protection," Kathleen Tober, a research scientist in OSU's pathology department, said in a prepared statement. "Our data suggests that while that may be a factor, an even more critical reason for this difference is that female skin may be better able to combat the damaging effects of UV exposure."

"Based on our data, it would be a reasonable hypothesis that one of the underlying mechanisms for this is that men might have less overall antioxidant levels and diminished DNA repair capacity," Tober said.

A third study found that black Americans may have a more difficult time giving up smoking, because they have much lower levels of an enzyme (glucuronide) that metabolizes nicotine and nicotine byproducts than whites. This means that blacks may experience higher nicotine levels when smoking, which makes it more difficult for them to kick the habit.

"Smokers adjust their level of smoking to maintain blood levels of nicotine, which are determined in part by rates of nicotine metabolism, and, while we can't say from this study that differences in metabolism definitively account for lower quit rates (among blacks), it could very well have an impact," Jeannette Zinggeler Berg, an M.D./Ph.D. student in biochemistry, molecular biology, and biophysics at the University of Minnesota, said in a prepared statement.

More information

The U.S. National Cancer Institute has more about cancer prevention.