The national food safety standard “Iodine Content of Edible Salt” (GB26878-2011) issued by the Ministry of Health will be officially implemented on March 15, 2012. This new standard stipulates that the iodine content per kilogram of salt must be between 20 mg and 50 mg, from which each province, autonomous region and municipality directly under the Central Government will choose the one suitable for the local situation according to the actual iodine nutrition level of the local population. The salt iodine content is selected by each province, autonomous region and municipality directly under the central government as the local standard according to the actual iodine nutrition level of the local population. “Scientific iodine supplementation” is a strategy for prevention and treatment that has not changed, which leads us to think: What are the dangers of iodine deficiency and excess iodine? What is the appropriate amount of iodine for human consumption? How can we monitor the nutritional status of iodine? What are the dangers of iodine deficiency and iodine excess? According to internationally recognized iodine research findings, the relationship between iodine intake and thyroid disease is U-shaped, with both high and low iodine intake leading to an increase in thyroid disease. If the body is deficient in iodine, it can seriously affect the health of the body. Iodine deficiency diseases are a series of damages caused by insufficient intake of iodine in the organism due to lack of iodine in the natural environment. The common ones are endemic goiter and endemic cretinism, which are mainly characterized by backward brain development and enlarged thyroid gland, and affect the intellectual and physical development of children and adolescents with iodine deficiency. Iodine deficiency in pregnant women not only seriously affects women’s physical and mental health, but also endangers the fetus, thus leading to miscarriage, premature birth, stillbirth, congenital malformations, and its main harm is to affect the brain development of the fetus, causing physical development disorders and intellectual impairment in the next generation in iodine deficient areas. However, with the improvement of living standard and material abundance, there are too many daily foods that are already “iodine supplemented” for us, and most Chinese people are no longer iodine deficient. While iodine deficiency has been greatly eliminated, iodine overdose can occur because everyone eats the same kind of salt – iodized salt. In 2002, an article in the American Journal of Endocrinology and Metabolism, a leading American medical journal, reported that excess iodine can lead to an increase in thyroid disease, and that increased iodine intake can lead to an increase in the incidence of autoimmune thyroid disease and papillary thyroid cancer. Since both iodine deficiency and excess iodine are harmful, what is the appropriate amount of iodine for the body to consume? From the point of view of iodized salt intake. The basic iodine requirement of the thyroid gland for the synthesis of physiologically necessary thyroid hormones is 60 μg/d. To eliminate all symptoms of iodine deficiency, a daily iodine supplement of 100 μg is very sufficient. The internationally recommended standards for iodine intake are 90 μg for infants and children aged 0-6 years, 100 μg for children aged 6-12 years, 150 μg for populations older than 12 years, and 200 μg for women during pregnancy or lactation. So, how do you monitor the nutritional status of iodine for appropriateness? The most common indicator used to evaluate the iodine nutritional status of a population is the median urinary iodine level (MUI), which can be checked at a hospital to clarify your iodine nutritional status. According to the World Health Organization (WHO), a median urinary iodine level (MUI) of <100 μg/L is insufficient iodine intake; 100-199 μg/L is adequate iodine intake (appropriate); 200-300 μg/L is excessive iodine intake; and >300 μg/L is excessive iodine intake. For those with excess iodine intake and iodine overdose, iodine intake should be restricted, especially for patients with thyroid disease, and the diet should be adjusted so that the urinary iodine is between 100 and 199 μg/L. From March 15 this year, the iodine content of salt will no longer be “one-size-fits-all”, and localities can add iodine within a floating range according to the actual iodine nutrition level of the local population. According to the results of environmental monitoring outside Jiangsu Province, except for Xuzhou Fengxian and Peixian counties and some towns in Tongshan, Suining and Pizhou, which are high iodine areas, other areas including Nanjing are mildly iodine deficient, and residents need to supplement iodine in their diet on a daily basis for a long time. It is reported that from March 15, Jiangsu will lower the iodine content of table salt, and the average level of iodine content will drop from the current 30 mg/kg to 25 mg/kg, allowing the iodine content to fluctuate from 18-33 mg/kg. Nanjing, as a mildly iodine-deficient area, will implement this new standard. In the province, Xuzhou Fengxian and Peixian counties and some townships in Tongshan, Suining and Pizhou are high iodine areas where iodine-free salt is implemented. For patients with thyroid disease, they can also consider buying non-iodized salt from special stores.