Dietary beta carotene and lung cancer risk in U.S. nonsmokers

Approximately 15% of all lung cancer deaths in the United States (about 22,350 deaths annually) may not be directly attributable to active cigarette smoking. Consumption of beta carotene, which is derived almost exclusively from intake of fruits and vegetables, has been associated with a reduced risk of lung cancer in smokers. However, studies examining this association in nonsmokers, particularly nonsmoking men, are limited.

The purpose of this study was to examine whether dietary factors including beta carotene and retinol are associated with a reduced risk for lung cancer in nonsmoking men and women.

A population-based, matched case-control study of lung cancer in nonsmokers was conducted in New York State from 1982 to 1985. Dietary interviews were completed for 413 individually matched case-control pairs of subjects. To determine whether the relationship between dietary intake from specific food groups and lung cancer differed by type of interview, smoking history, sex, age, or histologic type, we examined data on the case-control pairs from each subgroup separately. The intake of beta carotene and retinol was calculated as the weighted sum of the monthly frequencies of consumption of food items containing these nutrients, where the weights correspond to the nutrient content of a typical portion of the food items.

Consumption of greens (P for trend < .01), fresh fruits (P for trend < .01), and cheese (P for trend < .05) was associated with a significant dose-dependent reduction in risk for lung cancer, whereas consumption of whole milk (P for trend < .01) was associated with a significant dose-dependent increase in risk. Use of vitamin E supplements was also protective (odds ratio = 0.55; 95% confidence interval [CI] = 0.35-0.85). Increased consumption of the following food groups was associated with a reduction in risk among females: vegetables (P for trend < .025), raw fruits and vegetables (P for trend < .005), and dairy products (P for trend < .025). In males, increased consumption of raw fruits and vegetables was associated with a reduced risk for lung cancer (P for trend < .005). Dietary beta carotene (OR = 0.70; 95% CI = 0.50-0.99), but not retinol (OR = 0.98; 95% CI = 0.82-1.17), was significantly associated with risk reduction.

This is the largest study to date of dietary factors and lung cancer in nonsmokers; results suggest that dietary beta carotene, raw fruits and vegetables, and vitamin E supplements reduce the risk of lung cancer in nonsmoking men and women.