The relationship of physical activity with dietary cancer-protective nutrients and cancer-related biological and lifestyle factors.

The aim of the present study was to analyse the relationships among different intensities of leisure-time physical activity (PA) and cancer-protective dietary components, cancer-related biological (general and central obesity) and lifestyle factors (heavy smoking and excessive alcohol consumption). The present population-based cross-sectional study (765 men and 812 women from the general population of Gerona, Spain) included measurement of anthropometrical data, dietary intake, and alcohol and cigarette consumption and furthermore detailed evaluation of total leisure-time physical activity, including measurement of different intensities. Logistic regression analysis adjusted for several confounders was used to analyse the relationships among variables. A composite variable composed of dietary fibre, vitamin C, alpha-tocopherol, beta-carotene and folate was directly associated with higher levels of leisure-time PA in both genders, after further adjusting for energy intake [odds ratio (OR) of low versus second tertile of total leisure-time PA was 1.98 (95% confidence interval (CI) 1.22-3.23) for men and OR of low versus top tertile of total leisure-time PA was 1.75 (95% CI 1.07-2.84) for women]. Low to moderate- but not high-intensity leisure-time PA was directly related to higher intakes of these nutrients. Heavy smoking was inversely associated with higher levels of total leisure-time PA in men. With the exception of central obesity in women, there was no significant relationship between the cancer-related biological and lifestyle factors, and low to moderate-intensity leisure-time PA in both genders. In contrast, central obesity (OR 0.31, 95% CI 0.16-0.63) and heavy smoking (OR 0.38, 95% CI 0.16-0.96) were significantly related to high-intensity but not to total or low to moderate-intensity leisure-time PA in men and women, respectively. The observed relationships between leisure-time PA and several of the studied cancer-associated variables might partially account for the protective effect of physical activity against cancer observed in the literature. However, different intensities of leisure-time PA were distinctly associated with the mentioned cancer-related dietary, biological and lifestyle factors. Most importantly, although some of these variables were not associated with total leisure-time PA a significant relationship was observed for intensities of leisure-time PA. This should be considered when analysing the relationship between leisure-time PA and cancer.