DIET AND THE RISK OF PAPILLARY AND FOLLICULAR THYROID-CARCINOMA - A POPULATION-BASED CASE-CONTROL STUDY IN SWEDEN AND NORWAY

A population-based case-control study was conducted in two regions of Sweden and Norway to investigate the association between dietary habit s and the risk of thyroid cancer. The consumption of selected foods wa s reported in a self-completed food-frequency questionnaire by 246 cas es with histologically confirmed papillary (n = 209) and follicular (n = 37) thyroid carcinoma, and 440 age- and gender-matched controls. Od ds ratios (OR) and their 95 percent confidence interval (CI) were calc ulated as estimates of the relative risk using conditional logistic re gression. High consumption of butter (OR = 1.6, CI = 1.1-2.5) and chee se (OR = 1.5, CI = 1.0-2.4) was associated with increased risks. Resid ence in areas of endemic goiter in Sweden was associated with an eleva ted risk, especially among women (OR = 25, CI = 1.3-4.9). High consump tion of cruciferous vegetables was associated with increased risk only in persons who ever lived in such areas. A decreased risk was associa ted with consumption of iodized salt in northern Norway, and with use of iodized salt during adolescence among women (OR = 0.6, CI = 0.6-1.0 ). The results of this study suggest a role of diet and environment in the risk of thyroid cancer.