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.