Adapted dietary inflammatory index and differentiated thyroid carcinoma risk in two French population-based case-control studies.

PURPOSE: Thyroid cancer is the most common endocrine cancer and its etiology is still not well understood. The aim of the present study was to assess the association between an adapted dietary inflammatory index and differentiated thyroid cancer (DTC) risk in two population-based case-control studies (CATHY and YOUNG-THYR) conducted in France. METHODS: These studies included a total of 1321 DTC cases and 1502 controls, for which an adapted dietary inflammatory index (ADII) was computed based on food frequency questionnaires in each study separately. The association between ADII and thyroid cancer risk was assessed using logistic regression models controlling for potential confounders. RESULTS: Higher ADII scores, corresponding to a higher pro-inflammatory potential of the diet, were associated with higher DTC risk (odds ratio (OR) for 1 standard deviation (SD) increase: 1.09, 95% confidence interval (CI): 1.01, 1.18, P: 0.03). Associations were stronger in analyses restricted to women (OR for 1-SD increase: 1.14, 95% CI 1.04, 1.25, P: 0.005), as well as in women with lower education level, current smoking, or high body mass index. CONCLUSION: Our study suggests that a pro-inflammatory diet is associated with an increased risk of DTC, especially when combined with other inflammatory conditions such as tobacco smoking or overweight. Our findings will help better understand the role of diet-induced inflammation in DTC etiology.

Dietary Inflammatory Index and Differentiated Thyroid Carcinoma Risk: A Population-Based Case-Control Study in New Caledonia.

Despite research efforts, current knowledge of the etiology of thyroid carcinoma remains limited. To explore the potential role of diet-induced inflammation, we examined the association between differentiated thyroid cancer risk and the energy-adjusted Dietary Inflammatory Index (E-DII) in a population-based case-control study conducted in New Caledonia, a Pacific archipelago with one of the highest recorded thyroid cancer incidence rates in the world. The E-DII was computed from food frequency questionnaire information on usual dietary intake. 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. Positive associations between E-DII and thyroid cancer risk were observed (comparing extreme tertiles, odds ratio = 1.67, 95% confidence interval: 1.08, 2.58; P for trend = 0.002), with stronger associations found for larger carcinomas (P for trend = 0.0005). Stratified analyses showed an increased risk of thyroid cancer associated with the E-DII among Southern province residents (P for trend = 0.003), Melanesian women (P for trend = 0.02), obese participants (P for trend = 0.006), and ever-smokers (P for trend = 0.0005). Our results suggest that a proinflammatory diet-especially when concomitant with other inflammation-inducing conditions or habits (e.g., obesity, smoking)-is associated with increased risk of thyroid carcinoma.