Many patients ask me when they are discharged from the hospital if they can eat seafood after discharge, or ask directly if they can eat iodized salt. Other patients ask if thyroid tumors are caused by eating too much iodine, and if they can no longer eat iodine after surgery. This question cannot be answered in a broad-brush manner, starting with iodine requirements. 2007, the report “Monitoring and Evaluation of Iodine Deficiency Disorders Control” issued by the World Health Organization, the United Nations Foundation and the International Council for the Control of Iodine Deficiency Disorders, recommends that iodine intake varies according to age: for preschool children (0-59 months), the daily intake is 90 micrograms, for school-age children (6-12 years) at 120 micrograms per day, adolescents as well as adults at 150 micrograms per day, and pregnant and lactating women at 250 micrograms per day. The European Union and the Institute of Medicine in the United States have discussed the upper tolerable limit of iodine intake for adults and have stated that the upper tolerable limit is 600 micrograms per day and 1100 micrograms per day, respectively. Using our salt iodization rate of 35 µg/g and a per capita salt intake of 10 g/day, our daily intake of iodine is 350 µg. After deducting the losses from cooking and human metabolism, the iodine intake will not be higher than the WHO recommended amount. Even if we consider the differences between the European and American races and the Chinese physique and moderately lower the standard, the current daily iodine intake in China is still within the tolerable range. However, residents of coastal cities like Shanghai, especially those who consume a lot of seafood, already have sufficient iodine intake and do not need additional iodine supplementation, especially those who suffer from thyroid nodules and should consume as little iodine as possible. At present, there are more than 100 non-iodized salt supply points in Shanghai, but more than half of them are hospitals and pharmacies, so it is still inconvenient for the general public to buy non-iodized salt. People can stir-fry vegetables by popping the salt first, which allows the iodine in the salt to evaporate. However, if one insists on eating less iodine, one goes from one extreme to the other. It has been reported that the risk of thyroid cancer in children in iodine-deficient areas was three times higher after the Cherno nuclear event, and that the poorer prognosis compared to iodine-sufficient areas may be related to low iodine, and that iodine supplementation before or after radiation exposure may reduce the incidence of thyroid cancer in iodine-deficient areas after a nuclear event. It is clear that low iodine also increases cancer rates. In fact, studies have shown that the incidence of thyroid cancer is significantly higher in both iodine deficient and high iodine areas than in iodine normal areas. The difference in iodine intake correlates with the histological type of thyroid cancer: follicular carcinoma is more prevalent in iodine-deficient areas; papillary carcinoma is more prevalent in iodine-sufficient areas. Until a new national iodine supplementation program is introduced, it is currently recommended that those who love seafood should eat as little iodized salt as possible to avoid excessive iodine intake; those who do not eat seafood should not eat exclusively non-iodized salt to avoid too little iodine intake.