A population-based case-control study on fruit and vegetable intake and lung cancer: a paradox effect?

A population-based case-control study was carried out in Northwest Spain to analyze the effect of fruit and vegetable intake on the appearance of lung cancer. A non-significant protective association was found for overall consumption of leafy green and other vegetables, with consumption once a day or more vs. less than once a week yielding odds ratios of 0.63 [95% confidence interval (CI) = 0.24-1.63] for leafy green vegetables and 0.64 (95% CI = 0.30-1.36) for other vegetables. A significant protective association was found for potato consumption. No protective associations were recorded for fruit, whether overall or singly; instead, fruit consumption once a day or more vs. less than once a week registered a risk of 2.16 (95% CI = 1.02-4.58). Although the possibility that this effect may be due to a phenomenon of reverse causation cannot be ruled out, these results could support other reports and hypotheses which indicate that the protective effect of fruit might not be as pronounced as generally thought.