Diet, smoking and lung cancer: a case-control study of 1000 cases and 1500controls in South-West England

We have examined the relationship between diet and lung cancer in a case-co ntrol study of 982 cases of lung cancer and 1486 population controls in sou th-west England in which subjects were interviewed personally about their s moking habits and their consumption of foods and supplements rich in retino l or carotene. Analyses were performed for 15 dietary variables, including intake of preformed retinol and carotene. There were significant associatio ns (P < 0.01) with lung cancer risk for 13 of the variables, eight of which remained after adjustment for smoking. When the 15 variables were consider ed simultaneously, independent significant associations remained for 5: pre -formed retinol (increased risk), and fish liver oil, vitamin pills, carrot s and tomato sauce (decreased risk), It is unlikely that all five associati ons represent biological effects, or that they can all be explained by resi dual confounding by smoking, or by biases. We conclude that there is at lea st one as yet unidentified factor that is causally related to lung cancer r isk and of considerable importance in terms of attributable risk in this po pulation. (C) 2001 Cancer Research Campaign.