In our daily practice, we often hear patients with thyroid disease ask questions about iodine supplementation, and there are many vague or even wrong perceptions that need to be clarified. Why does the human body need iodine? Iodine is an essential trace element for the human body and is the main raw material for the synthesis of thyroid hormones. The thyroid gland is a very important endocrine organ in the human body, located in the middle of the front of the neck in the shape of a butterfly. The thyroid gland uses iodine and proteins to synthesize hormones, which improve the metabolic activity of the body, promote physical growth and brain development, and maintain all normal physiological functions of the human body. When iodine intake is seriously insufficient, the iodine reserve in the body decreases and the body synthesizes less thyroid hormones, resulting in insufficient metabolism and delayed growth and development. Why does iodine deficiency occur? Iodine in nature is widely distributed in rocks, soil, water and air, but water-soluble iodine in surface soil collects in seawater via rivers due to the scouring effect of rain. Therefore, crops such as grains and vegetables growing on land contain less iodine. The ocean is nature’s iodine reservoir, and seafood contains high levels of iodine. Iodine in human body mainly relies on daily diet for supplementation. Since land-based products in food are low in iodine, iodine deficiency will easily occur if land-based products are consumed singly. According to a survey conducted at the end of the last century, about 425 million people in China live in areas with severe iodine deficiency, accounting for 40% of the country’s total population. What are the dangers of iodine deficiency? Iodine is the raw material for synthesizing thyroid hormones. Iodine deficiency directly causes a decrease in the level of thyroid hormones, which are endocrine hormones essential for human growth and physiological metabolism, and their low level seriously endangers infants and children. There are two critical periods for brain development, one is from 10 to 18 weeks of gestational age, which is the period for neuroblastoma cells to proliferate, develop, differentiate, migrate and form brain tissue, and these developmental processes of neuroblastoma cells must be carried out with sufficient amount of thyroid hormone. These “branches” are the focal points and information channels for future thinking activities. Iodine deficiency during these two critical periods can cause a general loss of 5 to 10 IQs, which can lead to dullness in severe cases, and the damage to intelligence is irreversible. In addition, all tissues and organs of the body are adjusted by iodine and thyroid hormones during growth and development, and iodine deficiency can lead to delayed bone age, low weight, short stature and other consequences. How to supplement iodine scientifically? Salt iodization is the most reasonable and scientific method of iodine supplementation and the best way to prevent and treat iodine deficiency diseases. The superiority of salt iodization is mainly manifested in 4 aspects: 1. Residents living in iodine-deficient areas, whether adults, children or unborn fetuses, can benefit from it. Salt iodization can both prevent and treat various damages caused by iodine deficiency; 3. The amount of iodine added to salt can be strictly controlled and is given in the form of nutrients rather than in effective doses of drugs, which does not pose any medical dangers; 4. Economically, a family of three, with an increased expenditure of $1 to $2 per year, can be completely accepted. In the process of consumption, buy less at a time, not a lot of long-term storage; in a porcelain jar with a lid or brown jar, in a cool, dry place; without salt bursting the pot, salt when the dish is out of the pot to avoid volatilization of iodine at high temperatures. What is the amount of supplementation? The minimum daily requirement of iodine for a healthy person is 75 μg, and the more appropriate supply is twice as much. The United Nations Children’s Fund (UNICEF), the World Health Organization (WHO) and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) jointly recommend different daily supplies of iodine for different groups of people: 50μg for people within 1 year of age, 90μg for people between 2 and 6 years old, 120μg for people between 7 and 12 years old, 50μg for people over 12 years old and ****1, and 200μg for pregnant women and lactating mothers. China stipulates that the iodine content of table salt By iodizing salt, China has achieved the goal of eliminating iodine deficiency disorders in 2000, with a coverage rate of 93.8% of iodized salt and a qualified rate of 87.1% of iodized salt in residential households. On the other hand, there is a wide range of safe iodine intake for human beings, and from a medical point of view, iodine intake of up to 1000μg per day is safe. Who should not take iodine supplements? From the health point of view, the following groups of people should not take iodine supplementation: 1. people living in areas with high iodine levels or areas where high iodine goiter is prevalent, and people living in areas with high iodine levels in China with daily iodine intake of 800 to 1000 μg or more, do not need to take iodine supplementation because long-term continuous high iodine intake can cause high iodine goiter; 2. people with certain thyroid diseases, such as hyperthyroidism, should not take iodine supplementation; 3. people living in areas with severe iodine deficiency for a long time 3. People who live in areas with severe iodine deficiency for a long time should not take iodine supplementation too high and too fast, otherwise they will have a higher risk of developing iodine hyperthyroidism or other related thyroid diseases.