【英语时差8,16】为何食盐中含有碘？（在线收听）

 Pure, ordinary salt is simple. The scientific name for it is sodium chloride. But the label on a salt box shows that table salt usually contains more than just sodium chloride. Table salt often comes in “iodized” form — which means it includes a small amount of potassium iodide or sodium iodide. Iodized salt is intended to supply us with the trace amount we need of the chemical element iodine, which is necessary for the proper functioning of our thyroid gland. An iodine-deficient diet leads to enlargement of the thyroid gland, a condition called goiter. Severe iodine deficiency during pregnancy is also dangerous to the child.