1107Dietary polyphenol intake and differentiated thyroid cancer risk: a population-based case-control study in New Caledonia

Abstract

Abstract Background Aetiology of differentiated thyroid cancer is poorly understood. Among the risk factors strongly suspected to be involved in thyroid carcinogenesis are dietary factors. Recent evidence suggests polyphenols (i.e., natural bioactive compounds found in plant species), and their anticancer properties, may deserve closer epidemiological attention. Therefore, we examined the association between polyphenol intake levels and thyroid cancer risk in New Caledonia – a Pacific archipelago with some of the highest recorded thyroid cancer incidence rates in the world. Methods Food frequency questionnaire information from a population-based case-control study was used. Daily lignan and flavonoid intakes, expressed as aglycone equivalents, were estimated using Phenol-Explorer and relevant USDA databases. Unconditional logistic regression analyses were performed on data from 324 histologically confirmed cases of papillary or follicular carcinoma, diagnosed from 1993 to 1999, and 402 controls. Polyphenol intakes were analysed as both continuous and categorical variables (quartiles). Results Estimated median flavonoid and lignan intakes were 351.0 and 2.6 mg, respectively. When adjusting for sex, age, ethnic community, province of residence, BMI, smoking status, alcohol consumption and energy intake, no association with differentiated thyroid cancer risk was observed for flavonoids (OR = 1.06, 95% CI: 0.66, 1.70; comparing extreme quartiles), but a negative association was demonstrated for lignans (ORQ4vs.Q1=0.60, 95% CI: 0.37, 0.96; comparing extreme quartiles). Conclusions Our findings suggest that lignans may exert a protective effect on differentiated thyroid cancer. However, large-scale cohort studies and further analytical data on lignans are required to confirm this association. Key messages Lignans may play a role in thyroid carcinogenesis.