The Association between Dietary Intakes and Differentiated Thyroid Cancer: A Cross-Sectional Study among Patients and Healthy People in Iran

Background: Differentiated thyroid cancer (DTC) is the most prevalent endocrine cancer. Evidence showed a significant association between diet and DTC. Thus, this study aimed to assess the relationship between dietary intakes and DTC. Methods: This case-control study was accomplished among 300 adult patients and 300 matched (age and gender) controls in Mashhad city, Iran. Dietary assessment was conducted and the relationship between dietary intakes and DTC were examined by a validated food-frequency questionnaire and logistic regression analysis, respectively. Results: After adjusting for the confounders, a protective effect was observed for the highest tertile of low-fat dairy (OR=0.3, 95% CI=0.17-0.53, P < 0.001) and fruits' intakes (OR=0.28, 95% CI=0.15-0.52, P < 0.001) on DTC. However, the highest tertile of sugar intake was significantly related to greater DTC chance (OR=4.01, 95% CI=2.07-7.79, P < 0.001). A protective role was also found for vegetables in the second tertile of consumption (OR=0.3, 95% CI= 0. 0.17-0.54, P < 0.001) and for tea in the second and third tertiles (OR=0.2, 95% CI= 0.11-0.53, P < 0.001; OR=0.42, 95% CI=0.26-0.69, P = 0.001 respectively). However, the second and third tertiles of the roasted or fried meat consumption were significantly associated with higher DTC chance (OR=1.66, 95% CI= 1.007-2.76, P = 0.04; OR=1.92, 95% CI=1.07-3.42, P = 0.02 respectively). No significant association was detected for other dietary intakes. Conclusions: Consumption of low fat dairy, fruits, vegetables, and tea had a protective effect on DTC; whereas, roasted or fried meat and sugar consumption was significantly associated with higher DTC chance. Further studies are needed to confirm these results.