Why do some table salts need to be iodized?

Many types of table salt sold on the market are iodized. Why is iodine added to table salt? What role does iodine play in human health?

Iodine deficiency can cause goiter. Iodine is very important for human health. If there is a lack of iodine during the fetal period, it can lead to stillbirth, premature birth, and congenital deformities; if children and adolescents lack iodine, it can cause goiter (commonly known as "big neck disease"), hypothyroidism, and symptoms such as deafness, mental retardation, and stunted physical growth. Moreover, the harm caused by iodine deficiency to human health is often irreversible. Adding a certain amount of iodine-containing compounds, such as potassium iodide and potassium iodate, to table salt can play a preventive role in iodine supplementation through long-term consumption.

Iodine also has many other uses in the medical field. The most common is iodine tincture, which is used for disinfection and anti-inflammatory purposes. Iodine can launch a chemical "attack" on microorganisms, and microorganisms cannot develop resistance to it. The radioactive isotope of iodine, iodine-131, can be directly used for thyroid function tracking and the treatment of thyroid diseases; after preparation, iodine-131 can also be used as a scanning imaging agent for the liver, gallbladder, and kidneys.

Essential elements for human survival, such as iodine, are also known as life elements. Among them, the total amount of four elements—carbon, hydrogen, oxygen, and nitrogen—accounts for about 96% of the human body weight, and they mainly exist in the form of water and organic compounds; the content of seven elements—calcium, phosphorus, sulfur, potassium, sodium, chlorine, and magnesium—accounts for about 3.95% of the human body weight, and they are called macronutrients; while the content of 18 elements—iodine, iron, copper, zinc, manganese, fluoride, cobalt, chromium, molybdenum, selenium, nickel, vanadium, tin, strontium, rubidium, arsenic, silicon, and boron—is very low, and they are called trace elements.

Although trace elements account for a very small proportion of the human body weight, they each play an important function. Once there is a deficiency, it will affect human health and lead to disease. However, if the intake is excessive, it will also be harmful to health.