What are the pros and cons of edible salt?

The pros and cons of consuming iodized salt2009-08-23 16:25:08| Category: Health Tips| Tags: |Large font size

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Recently, many media have questioned the "universal salt iodization", believing that "excessive iodine supplementation" in some areas has led to an increase in thyroid diseases including thyroid cancer.

Our country was once one of the countries with the most serious iodine deficiency in the world. More than 700 million people were iodine deficient, accounting for 40% of the world's iodine deficiency patients.

In 1994, universal consumption of iodized salt was mandated as a national policy in China, similar to the family planning policy. At that time, the country promulgated the "Regulations on the Management of Salt Iodization to Eliminate the Hazards of Iodine Deficiency". Except for Beijing, Hebei, Shanxi, Jiangsu, Anhui, Fujian, Shandong and Henan, which are the eight provinces and cities with high iodine levels in the country, there is no need to enforce iodized salt. The remaining provinces All edible salt in the city is compulsorily iodized. In fact, in pursuit of profits, some local salt companies sell iodized salt in high-iodine areas.

How to understand "universal salt iodization"? Should the salt iodization strategy be adjusted?

In this regard, the relevant person in charge of the Bureau of Disease Control and Prevention of the Ministry of Health and Li Sumei, director of the National Iodine Deficiency Disease Reference Laboratory of the Chinese Center for Disease Control and Prevention, said that the current amount of iodized salt will be appropriately reduced next year.

The "People's Daily" reported that experts pointed out that the current iodine nutrition level of my country's population is generally in an appropriate state, but there are varying degrees of high water iodine problems in a few areas. Since 2007, the Ministry of Health has organized relevant experts to After conducting demonstrations, opinions on adjusting the current iodized amount of salt were initially formed, which were discussed and approved by the Professional Committee on Endemic Disease Standards in 2008. It is currently being submitted to the Food Additive Standards Professional Committee for review according to procedures, and then applied to the China National Standardization Committee for approval. It is estimated that the relevant adjustment plan will be officially announced in the first half of 2010.

1. Iodine deficiency and excessive iodine supplementation are both root causes of disease

Salt iodization is an important national measure to prevent and treat iodine deficiency diseases. In 1994, the country officially promulgated the Salt "Regulations on the Management of Iodization to Eliminate the Hazards of Iodine Deficiency", salt iodization has been fixed as a national policy. More than ten years later, why is iodized salt suspected of being a killer?

1. Iodine deficiency can cause disease

Under normal circumstances, the iodine reserves in the human body can be used for 2 months. In the early stage of iodine deficiency, iodine reserves and the body's strong regulatory mechanism can still be guaranteed The thyroid gland is functioning normally. After long-term iodine deficiency, the synthesis of thyroxine becomes difficult, eventually leading to health imbalance and a series of disorders, collectively known as iodine deficiency disease (IDD).

"Nandou Weekly" reported that the commonly known "big neck disease" is also an iodine deficiency disease. Under normal circumstances, thyroid tissue operates according to the body's demand for thyroid hormone. When the body's demand for thyroid hormone increases, thyroid follicular cells become active, colloid decreases, and epithelial cells become larger.

During iodine deficiency, due to insufficient raw materials for the synthesis of thyroid hormones, less thyroid hormone is synthesized. At this time, the hypothalamus and pituitary gland, which controls the thyroid gland, begins to secrete thyroid stimulating hormone to urge the thyroid cells to become active and meet the body's demand for thyroid hormone. As a result, thyroid cells begin to proliferate and become larger, forming a swollen "big neck" over time.

In addition, iodine cannot be ignored because it plays a role at a critical moment in brain development. During brain development, thyroid hormone is the main regulatory factor responsible for promoting the proliferation, migration, differentiation and functional improvement of neurons. Iodine deficiency and reduced thyroid hormone will lead to delayed brain growth and development, reduced brain weight, reduced sulcus, thinning of the cerebral cortex, etc., resulting in low IQ in children.

2. Excessive iodine can also cause disease

Everything in the world has two sides. Excessive iodine and lack of iodine can cause hypothyroidism. In 2008, 6 graduate students including Sang Zhongna of Tianjin Medical University conducted a clinical experiment on the safe intake of iodine for adults. Within 4 weeks, the researchers divided 161 healthy people with normal thyroid function into 7 groups. Take iodine ranging from 500 to 2000 micrograms.

Since excess iodine can be excreted from the body with urine, researchers can judge the body's iodine demand based on the amount of urinary iodine in the experiment.

Through blood and urine tests, researchers from Tianjin Medical University found that at the beginning of iodine supplementation, the urinary iodine levels of each group of people increased significantly, and the thyroid-stimulating hormone in the serum increased significantly, reaching 1 to 2 times the normal level, but the thyroid gland still worked normally. , 2 weeks later, subclinical hypothyroidism began to appear.

In fact, the thyroid gland has a strict control mechanism for iodine intake to prevent iodine from causing damage to the human body. In recent years, research at home and abroad has confirmed that the uptake of iodine by thyroid cells is regulated by the sodium-iodine transporter (NIS). NIS is a glycosylated membrane protein that plays the role of a transporter in the body and is mainly responsible for transporting iodine from the blood to the thyroid cells. Delivering iodine makes the intracellular iodine concentration 20-40 times higher than that outside the cell. When the body takes in excess iodine, the body inhibits the production of NIS, thereby reducing the uptake of iodine.

In addition, the physiological functions of the thyroid gland are dually regulated by the brain and the thyroid gland. The brain regulates thyroid activity through the hypothalamus and pituitary gland secreting thyroid stimulating hormone, and the thyroid gland feeds back its own needs to the brain. This mechanism is also To a certain extent, it ensures that the body absorbs iodine according to physiological needs.

Although excess iodine cannot double the iodine content in the body, if the high iodine state persists, the sodium-iodine transporter (NIS) will continue to be at a low level in order to protect the body from damage. , a large amount of iodine cannot be used and is eventually excreted in the urine. Over time, the amount of iodine in the thyroid tissue decreases, and so does the amount of thyroid hormone. At this time, in order to maintain the normal operation of the thyroid gland, the body increases the content of NIS and increases the supply of iodine. As a result, the body's repeated tossing between self-regulation and the inhibitory effect of high iodine eventually occurs, resulting in thyroid damage and adverse reactions such as high iodine goiter.

3. Complications from high-dose iodine supplementation

By the large-scale iodine supplementation policy in 2000, iodine deficiency diseases in my country were basically under control. However, a series of complications of iodine supplementation have emerged in areas that were once iodine deficient. Although there is no conclusion yet, the medical community generally believes that iodine supplementation will indeed bring some side effects. For thyroid cells that are long-term iodine deficient, sudden iodine is not a savior, but a killer!

As early as 1983, scholar MonM.C discovered in animal experiments that excess iodine may be toxic to iodine-deficient thyroid cells after being oxidized and organicized. In 2003, Master Luo Yuyu of Tianjin Medical University conducted a set of animal experiments and administered 5 to 50 times the physiological reagent iodine intake to iodine-deficient mice. The results showed that for mice that have been iodine-deficient for a period of time, , if the enlarged thyroid gland is suddenly exposed to high doses of iodine, necrosis of thyroid follicular epithelial cells may be induced.

Human beings are born with a stronger ability to adapt to the environment. After long-term iodine deficiency, the thyroid tissue "will be subject to foreign military orders" and form functionally autonomous thyroid nodules, which will no longer obey the brain. instructions, and make as much thyroid hormone as possible based on iodine reserves. At this time, if you suddenly supplement iodine, your body will produce too much thyroid hormone. This symptom is medically called "iodine-induced hyperthyroidism (IIH)" and is the most common complication of iodine supplementation. In addition, autoimmune thyroid diseases are more common.

The World Health Organization believes that the optimal state of iodine nutrition is when the urinary iodine level of the population is between 100 and 200 micrograms per liter. In this state, the incidence of iodine deficiency diseases and high iodine diseases is the lowest. A level above 300 micrograms per liter is considered excessive iodine intake. An intake of 150 micrograms/day is considered appropriate.

2. Salt iodization is a national policy. my country was once the country with the most iodine deficiency.

China was once one of the countries with the most serious iodine deficiency in the world, with more than 700 million people lacking iodine. , once accounted for 40% of the world's iodine deficiency patients.

As a result, in 1994, universal consumption of iodized salt was implemented as a national policy in China, similar to the family planning policy. At that time, the country promulgated the "Regulations on the Management of Salt Iodization to Eliminate the Hazards of Iodine Deficiency". Except for Beijing, Hebei, Shanxi, Jiangsu, Anhui, Fujian, Shandong and Henan, which are the eight provinces and cities with high iodine levels in the country, there is no need to enforce iodized salt. The remaining provinces All edible salt in the city is compulsorily iodized. In fact, in pursuit of profits, some local salt companies sell iodized salt in high-iodine areas.

3. Coastal provinces and cities are suspected of causing a sharp increase in thyroid disease due to excessive iodine supplementation

News from Singtao Global Network: In May 2009, a "Iodine Nutritional Status of Residents in Coastal Areas" The investigation was led by the Ministry of Health and carried out in a low-key manner in four provinces and cities: Zhejiang, Liaoning, Fujian and Shanghai. Iodized salt, which was supposed to prevent big neck disease, has instead led to an overdose of iodine among citizens, posing huge health risks. Recently, southern cities, especially coastal cities, have begun to reflect on the need for universal iodine supplementation. One media even put forward the shocking theory that "iodized salt causes disease."

"Chongqing Evening News" reported that today, 15 years after the implementation of the universal iodine supplementation policy, calls for independent iodine supplementation from the private sector and the medical community are getting louder and louder. Is the frequent occurrence of thyroid disease related to excessive iodine nutrition? China’s “one-size-fits-all” salt iodization policy may face deep adjustments.

4. Excessive iodine increase in thyroid disease is regarded as an important factor

With the spread of the slogan "Eat iodized salt, the whole family will be healthy!", the complex situation of iodine nutrition in various places has been Severely underestimated. Across the country, especially in coastal areas, the salt iodization policy has been increasingly questioned.

In cities such as Tianjin, Shenyang, Fuzhou, Guangzhou, and Shanghai, a large number of medical surveys show that thyroid diseases are increasing dramatically every year, and iodine excess is regarded as an important factor.

Cui Gonghao, a professor at Zhejiang University School of Medicine, said that a report from the Chinese Nutrition Society showed that the average daily salt intake of urban residents in China is 11 grams, and that of rural residents reaches 17 grams. This means that based on the calculation that most iodized salt currently on the market contains 20 to 50 micrograms of iodine per gram of salt, the Chinese people’s daily iodine intake has reached an astonishing 220 to 850 micrograms, far exceeding the 200 micrograms/g prescribed by the World Health Organization. Heaven's safety line.

5. One-size-fits-all iodine addition should be modified and the amount of iodine added should be adjusted according to local conditions

“In the context of the national iodine supplementation campaign, the health of the 500 million iodine-sufficient population has been completely ignored.” Cui Gonghao said. Big cities and coastal areas are mildly iodine-deficient areas. The population's dietary structure contains more protein and iodine-rich foods than other areas. There is room for lowering the iodine concentration of salt for the entire population.

In May this year, the Ministry of Health held an emergency meeting on the issue of iodized salt and decided to launch a census on the "iodine nutritional status of residents in coastal areas" in Zhejiang, Fujian, Liaoning, and Shanghai. The policy proposed by the census is "scientific iodine supplementation and classified guidance." Yang Yuexin, deputy secretary-general of the Chinese Nutrition Society, explained that "categorical guidance" means that the amount of iodine added to table salt should be adapted to local conditions.

In fact, a scientific research team led by Teng Weiping, the former president of China Medical University, conducted a five-year project on "The Impact of Iodine Intake on Thyroid Disease" starting in 1999 and concluded that Shown: Both iodine deficiency and iodine enrichment can lead to thyroid disease. During the "Two Sessions" in 2002, Professor Teng Weiping, then a representative of the National People's Congress, took the lead in submitting a bill proposing to amend the national salt iodization regulations.

6. Many experts suggest that non-iodized salt can be gradually supplied

“We have also been eating iodized salt for a long time. Will it cause excessive iodine?” Regarding the question in the south, especially in coastal cities, Reflecting on universal iodine supplementation, some citizens in Chongqing also raised concerns.

Chongqing is one of the key areas for iodine deficiency diseases in China. Since 1997, Chongqing has adopted various methods such as unified supply of iodized salt to eliminate iodine deficiency diseases. Up to now, the iodized salt coverage rate in Chongqing has reached more than 90%. Only districts and counties such as Fengdu have iodized salt coverage rate below 90%. According to the "Healthy Chongqing" health action plan, Chongqing will eliminate iodine deficiency diseases in 2012.

Xiao Bangzhong, deputy director of the Municipal Center for Disease Control and Prevention, said that before 1997, iodine deficiency diseases were quite serious in Chongqing, with Wulong, Chengkou, Qianjiang, Wuxi, Wushan and other places being the most prominent. As an evaluation indicator of iodine deficiency disease, the thyroid enlargement rate in children reaches 45%, and the urinary iodine level is 57 micrograms per liter. After more than 10 years of hard work, iodine deficiency diseases have been basically eliminated in Chongqing. The goiter rate in children has dropped to less than 10%, and the urinary iodine level is more than 200 micrograms per liter.

In response to concerns about "iodized salt causing disease", Xu Zhiming, director of the Marketing Department of the Municipal Salt Administration Bureau, said that it is healthy and safe for Chongqing people to consume iodized salt.

According to reports, if citizens need to buy non-iodized salt, it is very convenient. Salt companies in 40 districts and counties in Chongqing supply and sell non-iodized salt. Consumers only need to bring the hospital Proof available for purchase.

But Xu Zhiming said: "There are not many people with excessive iodine in Chongqing, and the sales volume of non-iodized salt in recent years is less than half a ton."

"Places such as Fuling and Fengdu have low iodized salt coverage and iodized salt In areas where deficiency diseases are more serious, the supply of iodized salt should be further strengthened. "Xiao Bangzhong, deputy director of the Municipal Center for Disease Control and Prevention, believes that judging from the current elimination of iodine deficiency diseases and the current coverage of iodized salt in Chongqing, most areas in the main city are weak. Residents have completely escaped the troubles of iodine deficiency disease. He suggested that the main urban areas can gradually implement non-uniform supply of iodized salt. Residents can choose to purchase iodized salt and non-iodized salt according to their own conditions to ensure their own health.

7. Add neither too much nor too little iodine

Iodine exists in nature, and people mainly absorb it from drinking water, food, vegetables and the surrounding environment. Infants and young children under 4 years old need 70 micrograms of iodine per day, adults on average need 150 micrograms per day, and pregnant women and nursing mothers need about 200 micrograms per day.

Iodine deficiency in children can lead to mental retardation and short stature. In adults, iodine deficiency can lead to fatigue and body edema, leading to endemic goiter, commonly known as "big neck disease". Excessive iodine intake can also be harmful to health. It can cause side effects and even cause iodine hyperthyroidism and other thyroid diseases.

It is a difficult challenge for everyone to achieve just the right amount of food. After all, eating and drinking cannot be moved from the restaurant to the laboratory. You can do it with a measuring cylinder and measuring cup.

Residents in non-iodine deficient areas do not need to consume iodized salt. For example, some counties in Heze, Shandong, are high-iodine areas and have canceled mandatory iodine supplementation; there are also fishermen who rely on seafood as their staple food. According to calculations, people who consume more than 750 grams of marine fish per day do not need to supplement iodine.

Tip:

Patients with hyperthyroidism do not need to consume iodized salt, because iodine supplementation will increase the synthesis of thyroid hormone and aggravate the condition.

Patients with thyroiditis (Hashimoto's disease) should not consume iodized salt. iodine supplementation will aggravate the symptoms of inflammation.

For patients with thyroid tumors, current medical research is still unclear on the relationship between thyroid cancer and iodine nutritional levels. Therefore, patients with thyroid cancer should be more cautious when consuming iodized salt, and follow the doctor’s advice based on their condition.

For patients with hypothyroidism (hypothyroidism), there is also controversy as to whether this group of people need supplementation, because the causative factors of hypothyroidism are diverse and cannot be generalized.

Patients with other thyroid diseases usually believe that only patients with goiter need iodine supplementation, but in fact both iodine deficiency and iodine excess can induce thyroid disease, so it is still necessary to combine the disease and their own iodine nutritional status. Make your choice under the guidance of your doctor.

Pregnant women and lactating women with thyroid disease are a difficult problem. The iodine nutritional level is closely related to the intellectual development level of infants and young children. It is necessary to follow the doctor's advice based on the individual situation, or to take separate measures during lactation. Methods of iodine supplementation for infants and young children.

Residents in iodine-deficient areas must consume iodized salt scientifically and for a long time. Otherwise, once iodized salt is stopped, iodine deficiency disease will recur.

Don’t buy too much iodized salt each time, because the iodine element is easy to volatilize over time.

The container for iodized salt should be covered and placed in a dry, light-shielded and high-temperature place.

Add iodized salt when the dishes are about to be cooked. Do not use iodized salt to fry the pot, stew for a long time, or cook for a long time, because iodine is easy to volatilize.