碘在胃肠道内是以离子形式被人体吸收。也就是说碘离子才是人体“有用之碘”。人体缺碘主要是由于环境缺碘引起。自然界中，碘元素通常以化合物的形式存在，一般可溶于水。如果人们所生活的地区水质、土壤等缺碘，则本地所产的植物性食物和动物性食物等各种食品都含碘少。致使 Iodine is absorbed by the body in the form of ions in the gastrointestinal tract. In other words iodine ion is the body “useful iodine.” Iodine deficiency is mainly caused by lack of iodine in the environment. In nature, iodine is usually in the form of compounds, generally soluble in water. If people live in areas such as water, soil and other iodine deficiency, the local production of plant foods and animal foods and other foods contain less iodine. Cause