FOXE1 Polymorphism Interacts with Dietary Iodine Intake in Differentiated Thyroid Cancer Risk in the Cuban Population

Background: The incidence of differentiated thyroid cancer (DTC) is low in Cuba, and the contribution of dietary factors to DTC in this population has not been investigated so far. The aim of this study was to evaluate the relationship between dietary iodine intake and DTC with regard to the interaction with environmental factors or some common single nucleotide polymorphisms (SNPs), based on a case-control study carried out in Cuba. Methods: A total of 203 cases and 212 controls from the general population were interviewed face-to-face using the dietary intake questionnaire and the photo booklet from the E3N cohort. A specific food composition table was constructed for this study. For each parameter studied, the odds ratio (OR) was stratified on age group and sex, and further adjusted for dietary energy, smoking status, ethnic group, level of education, number of pregnancies, and body surface area. Results: The risk of DTC was significantly reduced with increasing consumption of fish (p = 0.04), but no association between total dietary iodine intake and DTC risk was evident (p = 0.7). This lack of significant association was true whatever the age, the smoking status, the dietary selenium intake, and the ethnicity (p > 0.05). DTC risk was positively and strongly associated with the number of copies in the minor allele (A) for SNP rs965513 near FOXE1 among people who consumed less iodine than the median (p = 0.005). Conclusion: Overall, the majority of the studied population had an optimal dietary iodine intake. DTC risk was inversely associated with high fish consumption. Furthermore, DTC risk was positively associated with the number of copies in the minor allele (A) of rs965513 among people who consumed less iodine than the median. Because these findings are based on post-diagnostic measures, studies with pre-diagnostic dietary iodine are needed for confirmation.