Lung Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Description of the Evidence
Factors of uncertain association with risk
The results of many case-control and prospective cohort studies show that individuals with high dietary intake of fruits or vegetables have a lower risk of lung cancer than those with low fruit or vegetable intake. In a systematic review of the evidence, the World Cancer Research Fund rates the evidence as "limited suggestive" that nonstarchy vegetable consumption decreases lung cancer risk and "convincing" that fruit consumption and foods containing carotenoids decrease lung cancer risk. However, a subsequent systematic review and meta-analysis limited to prospective studies that adjusted for cigarette smoking found the evidence for carotenoids to be equivocal.
While the focus has been on fruit and vegetable consumption and micronutrients, a wide range of dietary and anthropometric factors have been investigated. Anthropometric measures have been studied, indicating a tendency for leaner persons to have increased lung cancer risk relative to those with greater body mass index.[42,43] The results of a meta-analysis showed that alcohol drinking in the highest consumption categories was associated with an increased risk of lung cancer.
Studies of dietary factors have yielded intriguing findings, but the fact that the diets of smokers tend to be less healthy than those of nonsmokers makes it challenging to separate the influence of dietary factors from the effects of smoking. When considering the relationships between lung cancer and dietary factors, confounding factors related to cigarette smoking cannot be dismissed as a possible explanation.
A meta-analysis of leisure-time physical activity and lung cancer risk revealed that higher levels of physical activity protect against lung cancer. The overall evidence for physical activity has been mixed, but several studies have reported that individuals who are more physically active have a lower risk of lung cancer than those who are more sedentary,[46,47,48] even after adjustment for cigarette smoking. The World Cancer Research Fund evidence review rated the inverse association between physical activity and lung cancer as "limited suggestive" evidence.
Studies of physical activity yield findings consistent with an inverse association, but the fact that physical activity behaviors differ between smokers and nonsmokers makes it difficult to infer that there is a direct relationship between physical activity and lung cancer risk.