Residents are scientifically supplemented with iodine
Knowledge quiz
01 What is an iodine deficiency disorder? What are the main harms of iodine deficiency?
Iodine deficiency disease is a general term for a group of diseases and hazards manifested by iodine malnutrition in the body caused by iodine deficiency in the natural environment. These include: endemic goiter, endemic cretinism (with dementia, short stature, deafness, muteness, and paralysis as the main clinical features) and endemic subclinical cretinism (with mental retardation as the main clinical feature), simple deaf-mute, fetal miscarriage, preterm birth, stillbirth, and congenital malformations.
In iodine-deficient areas, due to the different degrees of iodine deficiency in individuals, there is a spectrum from mild to severe, and the corresponding manifestations of iodine deficiency are different at different developmental stages. The main hazards of iodine deficiency in the fetal period are miscarriage, preterm birth, stillbirth, congenital malformations, endemic cretinism and endemic subclinical cretinism. The main harms of neonatal iodine deficiency include increased neonatal mortality, hypothyroidism, and retardation of the brain and body. Children and adolescents are more sensitive to iodine deficiency, which can affect intellectual development and physical development, resulting in motor, visual and auditory impairments, and the prominent manifestation is goiter. Iodine deficiency in adults can lead to hypothyroidism, goiter, etc.
02 Who is most vulnerable to iodine deficiency?
Pregnant women, lactating women, infants and young children aged 0-3 years, pre-school and school-age children are the most vulnerable to the dangers of iodine deficiency.
Pregnant women's demand for iodine is much higher than that of ordinary women, and the iodine ingested by pregnant women not only meets their own physiological needs, but also provides iodine to the fetus to ensure the growth and development needs of the fetus. Iodine deficiency in the natural environment, pregnancy reactions in pregnant women, and salt avoidance can all lead to insufficient iodine intake in pregnant women. As the fetus grows, the need for iodine increases in pregnant women. Because the iodine in the mother's body must be supplied to herself and the fetus at the same time, once the mother's iodine intake is insufficient, it will lead to iodine deficiency in the fetus, resulting in brain development disorders.
Infants and young children are in the second critical period of brain development and are as sensitive to iodine deficiency as their fetuses. Severe iodine deficiency in the fetus that persists into infancy develops into typical cretinism. If the degree of iodine deficiency in infants and young children is mild, they may become patients with subclinical cretinism or have only mild mental retardation, which can manifest as unresponsiveness to people and things around them, low motor ability, and delayed intelligence and growth and development. The iodine supply of infants and young children mainly comes from breast milk, and the mammary glands have the function of concentrating iodine. At this time, the iodine ingested by breastfeeding women is supplied to themselves and infants at the same time, and they are also sensitive to iodine deficiency, and once iodine deficiency will affect the growth and development of infants and young children.
Children and adolescents are in a period of very rapid growth and development, and the need for iodine has increased significantly, and they are more sensitive to iodine deficiency, which can cause damage to growth and development, including intellectual development and physical development. Children in iodine-deficient areas do not develop intellectually at the level they should. Iodine deficiency in children during growth and development can lead to delayed or delayed physical development, such as short stature, skeletal muscle dysplasia or retardation, epiphyseal dysplasia or delayed closure, delayed or delayed sexual development, and decreased learning ability. The prominent manifestation of iodine deficiency in children and adolescents is goiter. Thyroid volume increases with age, and during adolescence due to increased iodine requirements, physiologic onychoma is predisposed to. After iodine supplementation, the enlarged thyroid gland can return to normal after a period of time.
03 What is the prevalence of iodine deficiency diseases in mainland China?
The continent was once one of the countries where iodine deficiency disorders were more widespread and severe. In the 70s and 80s of the last century, the state organized a comprehensive investigation of the natural environment in various wards and counties across the country, measured the iodine content of water, and investigated the prevalence of iodine deficiency diseases (mainly including endemic goiter and endemic cretinism). Surveys show that there are about 35 million patients with endemic goiter caused by iodine deficiency and 250,000 patients with endemic cretinism. By the 90s of the last century, there were still nearly 8 million patients with endemic goiter and 187,000 patients with typical endemic cretinism in the country. The IQ of school-age children in iodine deficiency wards is on average 12.45 points lower than that in non-wards, and about 5%-15% of children in severe wards have mild mental retardation.
Surveys in the 70s and 80s of the last century found that the environment of 31 provinces, autonomous regions and municipalities directly under the central government (hereinafter referred to as provinces) was generally deficient in iodine (the median iodine in water was less than 10 micrograms/liter), and there were varying degrees of iodine deficiency disease epidemics in other provinces except Shanghai. According to the results of the 1994 survey on iodine nutrition status in the top ten cities in mainland China, the iodine nutrition of school-age children in Shanghai is deficient (median urinary iodine is 71.3 μg/L), and Shanghai is also an iodine deficiency area. Since the widespread iodization of salt in 1995, the mainland has carried out 14 national iodine deficiency disease surveillance. According to the national iodine deficiency disease surveillance, in 2022, the rate of qualified iodized salt consumption of residents increased from 39.9% in 1995 to 91.2%, the rate of goiter in children aged 8-10 decreased from 20.4% in 1995 to 1.5%, the overall iodine nutrition of the population was at an adequate level (the median urinary iodine of children aged 8-10 years was 212.4 micrograms/L), and the number of provinces with iodine malnutrition in the population (the median urinary iodine of children aged 8-10 years was less than 100 micrograms/L) decreased from 5 in 1995 to 0.
04 Why is iodine an essential trace element?
Iodine is an essential trace element in the human body, and the content in the human body is only 20-50 mg (average 30 mg). Although the content is very low, it is indispensable for the development of various body systems, especially the nervous system.
Iodine is an important raw material for the synthesis of thyroid hormones, which the thyroid gland needs every day to synthesize thyroid hormones. When iodine intake is stopped, the body's iodine reserves are only sufficient for 2-3 months. The body's iodine is completely dependent on the supply of the natural environment, and once it is deficient, it will cause insufficient thyroid hormone synthesis in the body, resulting in some clinical or subclinical symptoms, such as: weakness, lack of energy (physical and mental power), lack of concentration, fatigue, and decreased work efficiency. The main harm of iodine deficiency is to affect the brain development and physical development of the fetus and infants aged 0-3 years, causing irreversible damage.
05 How much iodine does the human body need per day?
In 2023, the daily reference intake of iodine per person for healthy people released by the Chinese Nutrition Society is about 85 micrograms/day for infants aged 0-0.5 years, AI for infants aged 0.5-1 years is about 115 micrograms/day, the recommended intake (RNI) for children aged 1-11 years is 90 micrograms/day, RNI for 12-14 years old is 110 micrograms/day, RNI for children aged 15 years old (inclusive) and adults is 120 micrograms/day, and RNI for pregnant women is 230 micrograms/day. The RNI for lactating mothers is 240 μg/day. The recommended daily intake of iodine is the level of iodine that meets the needs of the vast majority of individuals (97%-98%) in a specific sex, age, and physiological group. Long-term intake of iodine at the recommended level of iodine can meet the body's need for iodine and maintain proper iodine stores and body health in tissues.
06 What is the distribution of iodine in the natural environment?
Iodine is found in low levels in most soils, rocks, and water. There are three main reasons for iodine deficiency in the natural environment: First, in the Quaternary glacial period, due to the melting of glaciers, ice water washed away a large number of iodine-rich mature soils, and the iodine content of the new soil formed by bare rocks is only one-tenth of the original mature soil, which causes the lack of environmental iodine in most parts of the world, which is the main reason for iodine deficiency in the natural environment. Second, the iodine deficiency in the soil is aggravated by flooding, which causes the iodine in the soil to be washed away along with the soil. Third, due to the destruction of vegetation, the surface soil is carried away by wind, sand, rain and rivers, resulting in the bare soil surface, resulting in iodine leaching and a large amount of loss, which is more obvious in mountainous areas.
07 What is the distribution of iodine in water in China?
From 2017 to 2018, the former National Health and Family Planning Commission organized a national survey on the iodine content of drinking water. The national survey is based on township, township and sub-district offices (hereinafter referred to as townships). Among them, the townships where the iodine content of water (i.e., the median iodine of water) was found to be greater than 10.0 micrograms/L in this or previous surveys, and the survey was carried out on a village-by-village basis. The results of the survey showed that the iodine content of water outside most areas of the mainland was low, the iodine content of water in all provinces and the XPCC was below 40.0 μg/L, and the iodine content in water in 95.8% of counties was below 40.0 μg/L (of which 85.1% of counties had iodine content below 10.0 μg/L). The iodine content of township water in the country is 3.4 micrograms/liter, 94.5% of the country's rural water iodine content is below 40.0 micrograms/liter (of which 83.6% of the rural water iodine content is below 10.0 micrograms/liter), 2.9% of the rural water iodine content is between 40.0~100.0 micrograms/liter, and 2.6% of the rural water iodine content is above 100 micrograms/liter. Therefore, the mainland should continue to adhere to the universal salt iodization strategy, and implement various prevention and control measures in accordance with the principles of adapting measures to local conditions, categorical guidance, and scientific iodine supplementation.
08 Why should universal salt iodization be implemented?
Iodine deficiency in the extracontinental environment was once one of the most widespread and serious countries where iodine deficiency diseases were prevalent. Since the 60s of the last century, the mainland has implemented the prevention and control strategy of salt iodization in areas with moderate to severe iodine deficiency. In 1991, the Government of the mainland committed to the international community to eliminate iodine deficiency diseases by the year 2000. In 1994, the State Council promulgated the Regulations on the Administration of Salt Iodization to Eliminate the Hazards of Iodine Deficiency. In 1995, the mainland implemented universal salt iodization measures, and it took only five years, and in 2000, the goal of eliminating iodine deficiency diseases was basically achieved in the whole country, and the mainland has continued to eliminate iodine deficiency diseases. According to the results of the 2020 national "three-year campaign" for the prevention and control of endemic diseases, 100% of counties in the country have achieved the goal of eliminating iodine deficiency diseases. Practice has proved that universal salt iodization is an effective public health measure to eliminate the harm of iodine deficiency.
09 Do people in large cities and coastal areas also need iodine supplementation?
People in both urban and rural areas can be affected by the dangers of iodine deficiency. In 1994, the results of a survey on the iodine nutrition status of school-age children in Harbin, Shenyang, Beijing, Shanghai, Jinan, Zhengzhou, Hefei, Fuzhou, Xi'an, and Wuhan showed that the median urinary iodine level of children in five cities, including Shanghai, was less than 100 micrograms/liter, and the lowest was only 57.0 micrograms/liter, which was iodine malnutrition. In seven cities, including Jinan, the rate of goiter in children was more than 5%, and the highest was 26.4%. Surveys have shown that large cities with relatively good nutrition and living standards also have iodine deficiency problems.
In 2009, the results of a survey on the dietary iodine intake of residents in coastal areas in four provinces and cities of Fujian, Shanghai, Zhejiang and Liaoning showed that the consumption frequency and consumption of iodine-rich foods such as kelp and seaweed were very low. 84.2% of the iodine in the diet of residents in coastal areas comes from iodized salt, only 13.1% of iodine comes from various foods (2.1% of which kelp, seaweed and marine fish account for a total of 2.1%), and 2.7% of iodine comes from drinking water. If uniodized salt is consumed, more than 97% of the population will have lower iodine intake than the recommended intake, and the risk of iodine deficiency is very high.
10 Who should not eat iodized salt?
Patients with autoimmune thyroid diseases (common hyperthyroidism, thyroiditis, etc.) can skip or reduce iodized salt as prescribed by the doctor due to the need for treatment. Residents living in areas with high iodine levels and who have not yet changed their water supply already receive higher doses of iodine from drinking water and food every day, and these people are not suitable for iodized salt. All localities shall, in accordance with national regulations, reasonably increase the number of special counters for non-iodized salt to facilitate the purchase of non-iodized salt by patients with thyroid disease.
11 What are the sources of iodine intake?
Iodine is an essential element for the human body, which cannot be produced in the body and needs to be obtained from the external environment. The main sources of iodine for mainland residents are iodized salt, food and drinking water. In areas with high iodine in water sources where iodized salt supply has been suspended, drinking water is the main source of iodine, contributing 89.8%-93.9% to iodine, and 6.1%-10.3% to various foods (kelp, seaweed and marine fish account for 1.8%-2.1% together).
At present, the iodine content of drinking water for the majority of the inhabitants of the mainland is 10 micrograms per liter or less, and in this case, if iodized salt is not consumed, the iodine intake from food and drinking water alone does not meet the recommended dietary intake. Taking adults as an example, according to the 2012 food intake of Chinese residents' nutrition and health monitoring, the daily iodine intake of the average adult from food and drinking water was 34.4 micrograms, and that of large cities was 41.6 micrograms. Even in coastal areas where fish and shrimp intake is high, such as Shanghai, the dietary iodine intake of adult men and women is 70.4 micrograms and 65.5 micrograms, respectively, which is far lower than the recommended total daily intake of 120 micrograms. Therefore, eating normally without iodized salt alone cannot meet the body's daily iodine needs.
12 What is the iodine content in iodine-rich foods?
The iodine content of foods with high iodine content
| Name of the food | Iodine content (μg/100g edible part) |
| Nori (dried) | 4323 |
| Kelp (fresh) | 2950 |
| Dried shrimp (small prawns, dried) | 983 |
| Akamo | 162 |
| hairtail | 41 |
| Egg | 23 |
Data from the Guidelines for Iodine Supplementation for Chinese Residents
13 How can I determine if iodine nutrition is appropriate?
Since the iodine ingested by the human body is mainly excreted through urine after utilization, the urinary iodine level is often used as an important indicator to determine the iodine nutritional status of the population. In 2007, the World Health Organization (WHO)/United Nations Children's Fund (UNICEF)/International Council for the Control of Iodine Deficiency Disorders (ICCIDD, now IGN, Global Iodine Nutrition Alliance) recommended the following table for judging the iodine nutrition level of the population.
WHO/UNICEF/ICCIDD推荐人群碘营养水平判断标准
| Crowd categories | Median urine iodine (μg/L) | Iodine nutrient levels |
| child | <100 100－299* ≥300 | Iodine deficiency suitable Excess iodine |
| adult | <100 100－199 200－299 ≥300 | Iodine deficiency suitable Greater than the appropriate amount Excess iodine |
| pregnant woman | <150 150－249 250－499 ≥500 | Iodine deficiency suitable Greater than the appropriate amount Excess iodine |
| Breastfeeding women < 2-year-old infants | ≥100 ≥100 | suitable suitable |
Note: *Based on the 2018 UNICEF Guidelines for Monitoring Salt Iodization Programmes and Determining Iodine Nutrition in the Population.
For individuals, as long as they stick to iodized salt, they don't have to worry about iodine deficiency. The level of individual iodine intake can be judged from two aspects: one is estimated by dietary iodine intake, for example, the daily intake of iodine content of 25 mg/kg of iodized salt 6 grams, the supply of salt iodine is 150 (6×25) micrograms, plus the daily supply of iodine for food and water of 35-60 micrograms, the total iodine supply is 185-210 micrograms, deducting the loss rate of iodine in cooking by 20%, then, the iodine intake is about 148-168 micrograms, and then considering the bioavailability of iodine is 92%, 136-155 micrograms enter the bloodstream, which can meet the recommended daily dietary iodine intake of 120 micrograms for healthy adults, which is lower than the upper limit of daily iodine intake of 600 micrograms; The second is to measure the urine iodine content and refer to the above WHO/UNICEF/ICCIDD recommended standards. However, it is difficult to make a correct judgment about an individual's iodine nutrition level by taking a urine sample to test urine iodine. This is because it is difficult for a urine iodine measurement to reflect the average level of iodine intake. It is advisable to avoid eating or taking medications high in iodine for the first few days of urine collection, and to collect urine samples under normal dietary conditions, preferably a total urine sample for 24 hours. Due to the difficulty of collecting 24-hour urine samples, it is more convenient to collect random urine samples, but random urine samples cannot be collected only once, and it is best to collect at least 3 random urine samples at intervals for measurement, and make individual iodine nutrition status judgments based on dynamic observation results.
14 Why is salt iodization the best way to prevent and treat the dangers of iodine deficiency?
Iodine supplementation is the fundamental measure for the prevention and control of iodine deficiency diseases. Since iodine deficiency in the natural environment is long-term and the human body's ability to store iodine is limited, iodine supplementation should follow the principles of long-term, micro, daily and convenient. People can't do without salt every day, and iodized salt supplementation is in line with the principles of long-term, micro, daily and convenient. It has been proved in practice that salt iodization has the advantages of being safe, effective, simple, inexpensive, and can be adhered to for a long time, and is the best way to supplement iodine.
15 Why does the mainland need to adjust the salt iodine concentration in a timely manner?
Due to different dietary structures and dietary habits, the iodine content in iodized salt prescribed by countries around the world varies. Some countries use lower levels of salt iodine at 10-20 mg/kg and some countries have higher levels of salt iodine at 50-100 mg/kg.
With the change of dietary types and structure of mainland residents, the sources and proportions of iodine intake are also changing. In order to adapt to the changes in the sources of iodine intake and salt intake of residents, according to the results of the iodine nutrition level monitoring of the national iodine deficiency disease surveillance, the mainland has adjusted the salt iodine content three times, gradually adjusting the salt iodine content from the unified standard of 20 mg/kg or more for households (no upper limit is set) to 20 mg/kg, 25 mg/kg and 30 mg/kg, and authorizing all provinces and XPCC to choose their own iodine nutrition according to the actual iodine nutrition level of the population in their respective regions. At present, 14 provinces of Shaanxi, Hainan, Hubei, Guangxi, Jiangxi, Anhui, Yunnan, Shanxi, Jiangsu, Fujian, Inner Mongolia, Shandong, Zhejiang, and Jilin choose 25 mg/kg; Sichuan, Gansu, Guizhou, Xinjiang, XPCC, Qinghai, Hunan, Chongqing, Henan, Ningxia, Tibet, Tianjin, Shanghai 12 provinces and XPCC selected 30 mg/kg; Five provinces, Heilongjiang, Liaoning, Hebei, Beijing, and Guangdong, chose 25 mg/kg for the general population and 30 mg/kg for specific groups such as pregnant women.
16 How can residents properly buy and use iodized salt?
First, iodized salt should be purchased through formal channels, and the packaging must be clearly identified when purchasing.
Second, the purchased iodized salt should be properly preserved, should be placed in a cool and dry place, avoid direct sunlight and moisture absorption, and leave the stove for storage to avoid the impact of high temperature; The storage time should not be too long, and you can buy iodized salt in small packages, so that you can buy it at any time.
Third, in order to prevent iodine loss, iodized salt should not be put in too early during cooking, and it should be put in when the food is almost cooked; Avoid bursting the pot with iodized salt, stewing and boiling for a long time, so as to avoid the iodine being invalidated by heating and losing the effect of iodine supplementation.
17 Where are the areas high in iodine on the continent located?
There are two types of high iodine intake: waterborne and foodborne. The high iodine levels in mainland China are mainly water-based high iodine areas caused by high iodine content in drinking water. The mainland was the first country to discover water-borne hyperiodine goiter, which was first discovered in Bohai Bay, Hebei Province at the end of the 70s of the last century. From 1978 to 2013, water-borne areas with high iodine were found in nine provinces, including Hebei, Shandong, Shanxi, and Henan, and about 31 million people were at risk living in water-source areas and areas with high iodine disease. According to the 2017-2018 National Iodine Survey on Drinking Water Drinking Water, 2.1% (61) of counties in China had iodine content greater than 100.0 μg/L in county-by-county water. In townships, 2.6% (1050) of the country's township water had iodine content greater than 100.0 micrograms/L; At the village level, water iodine is greater than 100.0 micrograms per liter in 25,317 administrative villages across the country, covering a population of 40.65 million people.
18 What are the dangers of excessive iodine?
The hazards of iodine overdose include those caused by acute iodine overdose and chronic iodine overdose. The normal human thyroid gland has its own regulatory mechanism, and excessive iodine intake within a certain period of time generally does not cause obvious thyroid dysfunction. However, long-term excessive iodine intake can lead to thyroid autoregulation imbalance and thyroid dysfunction, goiter, hypothyroidism, etc., and may also induce or promote the occurrence and development of autoimmune thyroiditis. To date, there is no conclusive evidence that excessive iodine intake is associated with an increased risk of thyroid cancer.
Although pregnant women, lactating women, infants and young children are particularly in need of iodine supplementation, excessive iodine intake in these populations also has adverse health effects. Therefore, it is necessary to adapt measures to local conditions, classify guidance, and scientifically supplement iodine to keep all kinds of people in the appropriate iodine nutrition range as much as possible.
19 What are the main prevention and control measures of high iodine in water sources?
In areas with high iodine in water sources, residents drink water with too high iodine content, resulting in iodine intake exceeding the body's needs, and in severe cases, it can cause an increase in the incidence of high-iodine goiter, hypothyroidism and autoimmune thyroid disease. The prevention and control measures in areas with high iodine in water sources mainly include: the supply of uniodized salt by the salt industry sector; The water conservancy department implements water improvement and iodine reduction; Disease control, health, education, publicity and other departments jointly do a good job in health education, so that the masses can know how to buy salt; The disease control department has established and improved a monitoring system to keep abreast of the supply of uniodized salt, water iodine, and changes in disease in areas with high iodine in water.
20 Is iodized salt consumed after water supply in areas with high iodine in water sources?
After the water supply change in the water source high iodine area, it is necessary to strengthen the iodine nutrition and water iodine monitoring of the population in the area, and from the perspective of the population level, it is possible that the iodine nutrition level of residents in the area will show a downward trend after the water change. If the overall iodine nutrition of the population is still at a relatively appropriate level, the supply of non-iodized salt in the area can be maintained for further observation. Once the iodine level of the population has dropped to the level of iodine deficiency, the area needs to be resupplied with iodized salt. It is indispensable to do a good job in monitoring and health education, and to adjust prevention and control strategies in a timely manner.
21 Do I need to continue to consume iodized salt after the harm of iodine deficiency is eliminated?
The root cause of iodine deficiency is the lack of iodine in the external environment in which humans live, and the iodine content of animals and plants growing in this environment is also insufficient, so the iodine intake of people living in such areas is insufficient. The iodine in the soil and water sources is evaporated into the clouds by the iodine in the seawater, and then replenished to the land through rainfall, and the process of supplementing iodine through rainfall is quite slow, so the iodine deficiency state of the external environment of human life is long-term and difficult to change. According to the 2017-2018 national iodine monitoring results of domestic drinking water in mainland China, although it has been a long time since the Quaternary glacial period, the iodine content of drinking water in mainland residents is still low, and most areas of the country are still iodine-deficient areas.
Iodine is an essential trace element for the human body, and when iodine intake is stopped, the body's iodine reserves are only enough to last for 2-3 months. The mainland is a country with serious iodine deficiency, and if we cannot supplement iodine for a long time and continuously, iodine deficiency diseases will come back, so we must insist on long-term consumption of iodized salt.
22 How many countries in the world are iodized with salt?
According to 2021 data from the Global Iodine Nutrition Alliance, 145 countries or territories in more than 190 countries and territories have implemented salt iodization, of which 124 countries or regions have compulsory salt iodization and 21 countries have voluntary salt iodization. The iodine used in salt iodization in countries around the world is mainly potassium iodate or potassium iodide. According to the relevant literature, 98 countries or regions use potassium iodate, 26 countries or regions use potassium iodide, another 4 countries or regions allow the use of potassium iodate and potassium iodide, and 1 country uses sodium iodide. Among the countries that use potassium iodate in the production of iodized salt, there are both developing and developed countries.
23 Is potassium iodate safe as an iodine fortifier for table salt?
Because potassium iodate is more stable than potassium iodide, potassium iodate is used as an iodine enhancer for table salt in mainland China and most countries in the world. Since the implementation of universal salt iodization in 1995, iodine deficiency diseases have been completely controlled, and remarkable results have been achieved, indicating that potassium iodate iodized salt has achieved remarkable results in the prevention and treatment of iodine deficiency diseases. However, potassium iodate is an oxidizing substance, and its safety as a salt iodine enhancer has attracted social concern. However, potassium iodate iodized salt is not equal to potassium iodate. Research by the Institute of Nutrition of the Chinese Center for Disease Control and Prevention has confirmed that potassium iodate in iodized salt can be converted into iodine ions and iodine molecules (volatile loss) after cooking with various foods. Of these, 86.5% were converted into iodine ions and 13.2% into iodine molecules, with a total conversion rate of 99.7%. Therefore, after cooking or cold mixing of iodized salt for 30 minutes, potassium iodate almost no longer exists, and there is no need to worry about the safety of potassium iodate iodized salt. If the recommended daily intake of iodine for adults is 120 micrograms, theoretically 1 molecule of potassium iodate can oxidize 6 molecules of vitamin C, then the amount of vitamin C consumed by iodized salt is only 1.2 mg per day (taking vitamin C as an example, protein and other reducing substances in food can also react with potassium iodate). However, the average green vegetable contains tens of milligrams of vitamin C per 100 grams, so the potassium iodate in iodized salt consumes very little reducing substances in food and is unlikely to pose a health risk.
24 What is the change in the intake of cooking salt in mainland China?
The Report on Nutrition and Chronic Diseases in China (2020) released the changes in the intake of cooking salt in Chinese residents. The results of three national nutrition surveys from 2002 to 2017 showed that the intake of cooking salt showed a decreasing trend year by year (Figure 1). The average daily intake of cooking salt decreased from 12.0 g in 2002 to 9.3 g in 2015-2017, from 10.9 g in 2002 to 8.9 g in 2015-2017 for urban residents, and from 12.4 g in 2002 to 9.6 g in 2015-2017 for rural residents.
25 What is the relationship between salt reduction and iodine supplementation?
The World Health Organization's Sodium Intake Guidelines for Adults and Children (2012) and the Dietary Guidelines for Chinese Residents (2022 Edition) both recommend that adults consume no more than 5 grams of salt per day. According to the mainland "Iodine Content of Edible Salt" (GB 26878-2011) standard, if the iodine level of salt fortification is 25 mg/kg, the cooking loss rate is calculated according to the WHO recommendation of 20%, and the daily intake of iodine from iodized salt is 100 micrograms. Most of the mainland is iodine-deficient areas, the amount of iodine obtained from drinking water is about 10 micrograms per day, and the iodine content of the general population from food is about 25-50 micrograms per day, so the total iodine intake of the general population can reach 135-160 micrograms per day. Thus, children and adults consuming iodized table salt can still reach the recommended iodine intake per day, even under reduced salt conditions, while pregnant and lactating women are at risk of iodine deficiency. Therefore, it is recommended that pregnant and lactating women should choose iodized salt with high iodine content while reducing salt, and encourage the intake of iodine-rich foods, such as seafood, eggs, milk, etc.
There is no conflict between current salt reduction targets and salt iodine supplementation, but there is a need for countries to regularly monitor salt intake and salt iodine levels in the population so that the necessary adjustments to salt iodine levels can be made in a timely manner in response to observed changes in salt intake, and to ensure that people are getting the right amount of sodium and iodine at recommended levels.
26 What are the factors that affect the stability of iodine in salt?
Iodized salt is a salt that mixes a small amount of potassium iodate or potassium iodide with a large amount of salt for residents, that is, a means of bringing iodine into the body to meet people's physiological needs with salt as a carrier. The factors affecting the stability of iodine in salt are one of the important factors in determining the iodized content of table salt. Compared with potassium iodide, potassium iodate is chemically more stable and not easy to decompose. The available data show that the factors that may affect the stability of iodine in salt are: the variety of iodine fortifier added to edible salt, the source and variety of salt, the production and processing process of iodized salt, climatic conditions, the quality and form of packaging materials, cooking methods, etc.
27 What is a thyroid nodule?
Thyroid nodules refer to isolated or scattered lesions caused by abnormal growth of thyroid cells in the local area, and are a frequent and common disease of the endocrine system. Thyroid nodules can be detected by palpation or imaging: a mass found within the thyroid region on palpation; Imaging tests are usually done with thyroid ultrasound, which is a mass in the thyroid gland that is different from the echo of normal thyroid tissue. When there is a discrepancy between the palpation results and the imaging results, the imaging results shall prevail.
28 Is iodized salt consumption associated with thyroid nodules?
Thyroid nodules are common and are more common in women than men. Detection rates by palpation are 3% to 7% in the general population and can be as high as 20% to 76% with high-resolution ultrasound. According to the results of relevant surveys in mainland China, the detection rate of thyroid nodules with a diameter greater than 0.5 cm is 20.43%, and it will increase with age and body mass index, that is, the detection rate of older and obese people will increase.
China's Guidelines for the Diagnosis and Treatment of Thyroid Nodules and Differentiated Thyroid Cancer (Second Edition) (March 2023) only recommend screening for people with a history of radiation exposure to the head and neck in childhood, a history of systemic radiation therapy, a family history of thyroid cancer in first-degree relatives (parents, children), and a family or personal history of thyroid cancer-related genetic syndromes. Ultrasound screening for thyroid nodules is not recommended in the non-high-risk general population if there are no corresponding symptoms and signs; In addition, for nodules < 1.0 cm in diameter detected by ultrasonography, fine-needle aspiration biopsy is generally not performed unless there are signs of metastasis.
Long-term surveillance and related studies in mainland China have shown that iodine deficiency is a risk factor for thyroid nodules, and the detection rate of thyroid nodules in areas with common salt iodization is lower than that in areas with historical iodine deficiency. Currently, there is no evidence that iodized salt consumption is responsible for increased thyroid nodules. If the thyroid nodule is autonomous, iodine intake needs to be restricted.
29 What are the main causes of thyroid cancer?
At present, the cause of thyroid cancer is not clear, and the known risk factors include ionizing radiation, environment, diet, lifestyle, mental stress and other factors. The increase in the incidence of thyroid cancer in mainland China while the mortality rate has remained basically stable, which is inseparable from the improvement of clinical diagnosis and the progress of imaging technology.
30 Is iodized salt consumption linked to thyroid cancer?
Iodine deficiency is more likely to cause structural and functional changes in the thyroid gland than excessive iodine intake. This may be related to thyroid-stimulating hormone (TSH) stimulation of thyroid hyperplasia. Based on the cancer surveillance data of the National Cancer Registry and the monitoring data of the Chinese Center for Disease Control and Prevention, preliminary correlation analysis showed that iodized salt consumption was not correlated with the incidence and mortality of thyroid cancer.
(Source: "Tianjin CDC")