Possible Goitrogenic Effects of Selected Japanese Foods

Abstract

Goiters frequently develop among Japanese living along the seacoast despite high daily iodine intake. To evaluate possible goitrogenic effects of certain Japanese foods, groups of Wistar albino rats were fed, for 5 months, a low iodine basal diet (Remington ration) supplemented with Chinese cabbage, turnip, buckwheat noodle, soybean, or seaweed. Some of these supplemental foods already were known to be goitrogenic. Of 7 groups of rats one group was fed the Remington ration alone; another group received Remington ration supplemented with 2 μg iodide (as 2.4 μg sodium iodide) per rat per day. These 2 groups served as controls for the 5 test groups. Goiters developed in the rats of all groups except those fed seaweed. Goiter was not completely prevented by addition of 2 μg iodide to the Remington ration, apparently indicating that Remington ration increases iodine requirement. Foods supplementing the Remington ration did not produce goiters significantly larger than those observed in the controls. Histologically, goitrous thyroid tissue revealed hyperplastic follicles with scanty colloid, dissimilar to colloid goiter commonly occurring in man. Thyroid tissue of rats given seaweed or supplemental iodine was virtually indistinguishable histologically from normal rat thyroid. The experiment indicated goitrogenicity of the Remington ration but failed to demonstrate positively the goitrogenicity of supplemental foods. Response to the seaweed diet showed that ingestion of large amounts of iodine can prevent development of goiter.