Why people who eat seafood suffer from goiter?

This statement is incorrect. Seafood generally contains high levels of iodine, especially seaweeds like kelp, nori, wakame, dulse, which aids in preventing goiter by supporting the production of thyroid hormones. Iodine deficiency usually leads to goiter. However, consuming excessive iodine also may cause it due to the Wolff-Chaikoff effect and Jod-Basedow phenomenon. So maintaining the recommended dietary intake of iodine helps in avoiding complications related to thyroid health.