People who have quit smoking can further reduce their risk of developing lung cancer by adding lots of vegetables to their diet − as measured by eating four or more servings of salads a week − compared to people who quit but do not eat their veggies, report researchers at The University of Texas M. D. Anderson Cancer Center. The investigators also found that physical activity like gardening reduces risk of developing the cancer in "former-smokers" by up to 45 percent, compared to former smokers who don't garden.
"We are trying to understand what components of lifestyle can reduce lung cancer risk in people who have quit smoking − which has been a neglected field of study," said Michele Forman, Ph.D., a professor of epidemiology at the University of Texas. "Although this is a very preliminary analysis, it gives us some important clues about how everyone − smokers and non-smokers alike − might be able to reduce their risk of developing lung cancer."
The research team also found that current smokers have a two-fold higher risk of developing lung cancer if they eat three servings or less of salad a week, compared to current smokers who do eat four or more salads weekly. Reduction of risk through gardening was about the same (33 percent) as seen in former smokers, they found. The investigators are also exploring the role of diet and physical activity in lung cancer risk for never-smokers.
"If you are worried about lung cancer risk, this study shows that you may benefit from eating a healthy diet and being physically active," Forman said.
The data come from M. D. Anderson's case control study of lung cancer, involving more than 3,800 participants. Its unique design matches lung cancer patients at M. D. Anderson with participants who are treated at a Houston HMO and divides them by smoking status. So, for example, a person who has never smoked but who developed lung cancer would be matched with a never-smoker who is cancer-free, and the same pairing process is done for former and current smokers with and without lung cancer. All participants are non-Hispanic whites.
The model has already identified a variety of epidemiologic risk factors for lung cancer due to exposure to second-hand smoke and to dust, family history of cancer, history of respiratory disease in the patient and smoking history. With those variables, the discriminatory power of the model was modest.
This study added diet and physical activity to the list of potential factors, making it the first risk prediction model to address both of these variables at the same time, Forman says. To do that, investigators asked participants about eating salad "because salad is a marker for consumption of many vegetables," and polled participants about gardening activity "because we found that gardening is one of the few activities that people with lung cancer report doing," she said.
According to Forman, the researchers do not know yet whether those habits of eating well and exercising "are a marker for other lifestyle factors that might be even more important, such as lack of alcohol consumption. We have a lot of puzzles in the picture yet to analyze."