Dietary Patterns, Goitrogenic Food, and Thyroid Cancer: A Case-Control Study in French Polynesia

Abstract

French Polynesia has one of the world's highest thyroid cancer incidence rates. A case-control study among native residents of French Polynesia included 229 cases of differentiated thyroid cancer diagnosed between 1979 and 2004, and 371 population controls. Dietary patterns and goitrogenic food consumption (cabbage, cassava) were analyzed. We used a factor analysis to identify dietary patterns and a conditional logistic regression analysis to investigate the association between dietary patterns or food items and thyroid cancer risk. Two distinct dietary patterns were identified: traditional Polynesian and Western. A nonsignificant inverse association was observed between the traditional Polynesian dietary pattern and thyroid cancer risk. The Western pattern was not associated with thyroid cancer risk. Cassava consumption was significantly associated with a decreased risk of thyroid cancer. In conclusion, a traditional Polynesian dietary pattern led to a weak reduced risk of thyroid cancer in French Polynesia. The protective effect of cassava on this cancer does not seem to be substantially different from that of cabbage, which was the main goitrogenic food studied to date.

ACKNOWLEDGMENTS

This study was supported by the Association pour la Recherche contre le Cancer, the Ligue Nationale Contre le Cancer, the Direction Générale de la Santé, the Comité de radioprotection de Electricité de France, Agence Française de Sécurité Sanitaire et Environnementale et du Travail, CHILD-THYR EEC program, and the Fondation de France.

The authors thank John Paoaafaite and Joseph Teuri who contacted and interviewed cases and controls in the study. They are grateful to Dr Frédérique Bost-Bezeaud and Dr Patrice Petitdidier for having performed the pathological review of the cases. They are also grateful to Barbara Burlingame, leader of group “Nutrient requirements and assessment” of the Food and Agriculture Organization for the validation of the estimates of French Polynesian nutrients (in particular, energy) from the Pacific Islands food composition tables.