May 18th is National Iodine Deficiency Disorders (IDD) Prevention Day. China is one of the countries most severely affected by iodine deficiency, with approximately 720 million people living in iodine-deficient regions. In 1990, the Chinese government made a solemn commitment to eliminate iodine deficiency and successively formulated a series of laws and regulations, implementing comprehensive preventive and control measures centered on iodized salt. Currently, the consumption rate of iodized salt among Chinese residents has continuously increased, and iodine nutritional status has significantly improved and become more rational.
The trace element "iodine" is a vital element essential for the human body. The minimum daily iodine requirement for adults is no less than 100-150 μg. Due to differences in age and physiology, the iodine requirements vary among different populations: children under 4 need 70 μg per day, adults average 150 μg, while pregnant and lactating women require about 200 μg. A doctor from the Endocrinology Department of Friendship Hospital explained that all populations living in an iodine-deficient environment are susceptible to the harm of iodine deficiency. Among them, the most vulnerable groups are fetuses, infants, school-age children, pregnant women, and lactating women. Iodine is the primary raw material for the thyroid gland to synthesize thyroid hormones (T4, T3). T4 and T3 regulate and affect the metabolism of proteins, fats, sugars, vitamins, etc., and the growth and development of tissues and organs in the body. When the body's iodine intake cannot meet the physiological demand, the synthesis and secretion of T4 and T3 decrease, leading to a series of pathological damages, mainly including endemic goiter, endemic cretinism, premature birth, stillbirth, congenital malformations, deafness, muteness, and mental retardation. These damages are collectively referred to as iodine deficiency disorders.
The iodine required by the human body mainly comes from food. Natural iodine deficiency refers to insufficient iodine content in soil and drinking water. Due to the food chain, if soil and water (excluding seawater) are deficient in iodine, it leads to iodine deficiency in plants (grains or vegetables) and animals. When people consume iodine-deficient food, it results in insufficient iodine intake. The most common and effective method for iodine supplementation in daily life is consuming iodized salt, because iodized salt is relatively inexpensive, and the iodine contained in 5-6 grams of iodized salt per day can meet people's daily physiological needs. Currently, iodized salts at home and abroad are generally divided into two types: potassium iodate iodized salt and potassium iodide iodized salt. Most of the iodized salt in China currently is potassium iodate iodized salt, with some regions using potassium iodide iodized salt. These are collectively referred to as iodized edible salt. When cooking, we should try to add salt as late as possible to prevent the iodine in the iodized salt from evaporating due to prolonged heating.
Excessive iodine, like iodine deficiency, is harmful to human health and can cause adverse reactions such as iodine-induced goiter, and even lead to iodine-induced hyperthyroidism. It is a misconception among many people that "the more iodine supplementation, the better." To this end, China sells specially produced non-iodized salt in high-iodine areas, and with the support of local salt companies, has set up exclusive counters for non-iodized salt to protect people's health.
In recent years, excessive iodine has received great attention from the international thyroid and endemic disease communities. In 2001, an international authoritative academic organization first proposed the definition of excessive iodine (urinary iodine greater than 300 μg/L) and unanimously agreed that excessive iodine can lead to a significant increase in the incidence of hypothyroidism, autoimmune thyroid diseases, and papillary thyroid cancer. Experts believe that the recommended daily iodine intake for adults is 150 μg, and the median urinary iodine should be controlled between 100-200 μg/L to ensure that the iodine nutritional status of Chinese residents remains within a safe range, free from the harm of both iodine deficiency and excessive iodine.