Abstract
Background: Cervical cancer incidence is highest in developing countries in Asia and South America and is associated with relatively poor survival in these high-risk populations. Diet may influence susceptibility to and/or persistence of human papillomavirus infection, a necessary cause of cervical cancer. Soy isoflavones and green tea catechins have immunomodulating properties that may protect against cervical cancer.
Methods: We investigated the relationship between soy, green tea and black tea intake and risk of cervical cancer in the well-established prospective population-based Singapore Chinese Health Study. Soy and tea consumption data were collected at baseline using a validated food frequency questionnaire. Cervical cancer cases (n=257) were identified from 34,028 women followed for an average of 11.7 years. Proportional hazards regression methods were used to assess the associations between soy and tea intake and cervical cancer risk. Hazard ratios (HRs) and 95% confidence intervals (CIs) were adjusted for Papanicolaou (Pap) test history, education level, parity, use of oral contraceptives, and other potential confounders.
Results: A statistically significant inverse association was observed for highest versus lowest soy intake and cervical cancer risk (HR=0.71; 95% CI:0.53, 0.96; p for trend=0.03). Consumption of green tea on a weekly or more frequent basis, compared to no tea intake was inversely associated with cervical cancer risk (HR=0.80; 95% CI:0.56, 1.14; p for trend=0.2). There was no association with black tea. We observed interacting effects for soy and green tea intake on risk of cervical cancer. The inverse association with soy intake was stronger among women who drank green tea (HR=0.42; 95% CI:0.25, 0.69; p for trend=0.001). No association was observed for soy intake among non-tea drinkers (p for interaction=0.01).
Conclusions: We provide the first human evidence for individual, as well as synergistic protective effects of soy and green tea intake on risk of cervical cancer. These findings were independent of self-reported frequency of Pap testing and education level. Our findings support experimental evidence for immunomodulating effects of green tea catechins and soy isoflavones as a possible mechanism underlying the protective effect of these dietary factors on cervical cancer risk.
Citation Information: Cancer Prev Res 2011;4(10 Suppl):B97.