As early as 1990, the fao/IAEA/WHO expert committee proposed the concept of essential trace elements. The concept states that essential trace elements are physiologically active substances in the human body, essential components in organic structures, which must be ingested through food, and when the intake is reduced to a certain low limit, it will lead to one or some important functional damage. The expert committee classified iron (Fe), iodine (I), zinc (Zn), selenium (Se), copper (Cu), molybdenum (Mo), chromium (Cr), and cobalt (Co) as essential trace elements. Although these 8 elements account for a very small proportion in the human body, their role is indispensable. Today we will learn what key role these essential trace elements play in health.
Iron (Fe): Element 26, 4th Cycle 8th Subgroup
Iron is an important essential trace element of the human body, and the total amount of iron in the human body is 4 to 5g. Iron is a component of hemoglobin and myoglobin, cytochrome A and some respiratory enzymes, and is involved in the transport, exchange and tissue respiration of oxygen and carbon dioxide in the body. If iron intake is chronically inadequate or excessively lost, it can affect hemoglobin production, resulting in iron deficiency anemia. Long-term iron deficiency in children can lead to restlessness, low reflexes, inattention, poor memory, hyperactivity and other phenomena. However, when iron is stored in excess, it can also lead to a variety of diseases, such as heart and liver disease, diabetes and even some tumors.
Recommended intake: Iron can be reused by the body in the body's metabolism, usually the amount of iron excreted by the human body is very small, so as long as it is supplemented from food, it can meet the needs. The average absorption rate of iron in mixed diets is 10% to 20%, women lose about 2 mg of iron per day during menstruation, and the recommended amount (RNI) of adult dietary iron of the Chinese Nutrition Society is: 12 mg/day for men and 20 mg/day for women, and the maximum tolerable intake (UL) is 42 mg/day.
Main food sources: The main forms of dietary iron are heme iron and non-heme iron, the effective absorption rate of heme iron (divalent iron) is 15% to 35%, and non-heme iron (trivalent iron) needs to be reduced to divalent iron before it can be absorbed, and its effective absorption rate is only 2% to 20%. The iron content and absorption rate in general animal foods are high, such as animal liver, animal whole blood, livestock meat, fish, etc. are good sources of dietary iron. Although the iron content in rapeseed, amaranth and spinach is slightly higher, it is non-heme iron, and the utilization rate is low, which is not recommended.
Iodine (I): Element 53, cycle 5, main group 7
Iodine is one of the essential trace elements of the human body, adults contain 15 to 20mg of iodine, of which 70% to 80% are present in thyroid tissue. Iodine is mainly involved in the synthesis of thyroid hormones in the body, which have the effect of enhancing metabolism and promoting growth and development (especially brain development). Both iodine deficiency and iodine excess can cause damage to health. When the human body is iodine deficiency, it can lead to "iodine deficiency disease" (IDD) due to thyroid dysfunction. Iodine excess can induce or promote hypothyroidism and the development and development of autoimmune thyroiditis.
Recommended intake: Under conditions of stable and adequate iodine supply, the body's excretion of iodine is almost equal to the intake of iodine. The recommended amount (RNI) of adult dietary iodine of the Chinese Nutrition Society is 120 μg/day, and the maximum tolerateable intake (UL) is 600 μg/day.
Main food sources: Iodine is mainly found in food and water, of which seafood has a higher iodine content than terrestrial foods, and terrestrial animal foods are higher than plant foods. Kelp, seaweed, fish and shrimp and shellfish are common high-iodine foods, and iodized salt is also the best food to provide iodine stably. In some parts of 11 provinces such as Hebei, Shandong and Shanxi, about 30 million residents live in areas with high water iodine, in order to reduce the risk of iodine overdose in high-water iodine areas, the supply of iodized salt in high-water iodine areas has been completely stopped in 2012. In addition, patients with hyperthyroidism or hypothyroidism, Hashimoto's thyroiditis, etc., may skip or reduce iodized salt due to treatment needs.
Zinc (Zn): Element 30, cycle 4, subgroup 2
Zinc is known as the "flower of life". It is a component of more than 200 enzymes in the human body, directly involved in the synthesis of nucleic acids, proteins, cell differentiation and proliferation, and many important metabolisms. Zinc is an indispensable substance in important physiological processes such as human growth and development, intellectual development, reproductive genetics, immunity, and endocrine. When the total amount of zinc in the human body is reduced, it can cause damage to immune tissue, resulting in immune function defects. According to the survey report (2011) of authoritative units such as the Chinese Center for Disease Control and Prevention, about 60% of children in China are zinc deficient, and the zinc deficiency rate of pregnant women and nursing mothers is about 30%. However, long-term supplementation of a very large amount of zinc (100mg/day) can occur anemia, decreased immune function and copper deficiency.
Recommended intake: The recommended dietary zinc intake (RNI) of the Chinese Nutrition Society for each population is as follows: 3.5 mg/day for infants aged 6 to 12 months, 4 mg/day for 1 to 3 years, 5.5 mg/day for 4 to 6 years old, 7 mg/day for 7 to 10 years old, 10 mg/d and 9 mg/d for boys and girls aged 11 to 13 years, 12 mg/day and 8.5 mg/d for boys and girls aged 14 to 17 years, and 12.5 mg/day for males and female adults aged 18 years and older, and 12.5 mg/ d and 7.5 mg/d. The maximum tolerateable intake (UL) is 40 mg/day.
Main food sources: General plant foods have low zinc content, animal foods such as shellfish seafood, red meat, animal offal are excellent sources of zinc; cheese, shrimp, oats, peanut butter, peanuts, etc. are good sources; dried fruits, cereal germs and wheat bran are also rich in zinc.
Zinc supplement products: If zinc deficiency is diagnosed in the hospital, zinc supplements can be taken under the guidance of a doctor. Zinc supplementation products can be divided into three categories: inorganic zinc, organic zinc, and bio-zinc. Commonly used in clinical practice is organic zinc products, the main ingredients are a variety of amino acids zinc, zinc lactate, zinc licorice, zinc citrate, zinc gluconate, etc., because such chemical zinc may cause irritation to children's gastrointestinal tract, generally required to be taken after meals. Do not use zinc products as nutritional products for infants and young children to take large amounts for a long time.
Selenium (Se): Element 34, 4th cycle 6th main group
Selenium is an essential trace element, and lack of selenium can significantly reduce the body's immunity. Selenium-deficient areas are prone to endemic diseases such as Keshan disease and large osteoarthritis and cardiovascular and cerebrovascular diseases. Appropriate selenium supplementation has a significant improvement effect on cancer, cataracts, and malnutrition in children, and can avoid the occurrence of diseases such as arteriosclerosis, hypertension, myocardial infarction, senile neurological insufficiency, memory and intellectual disability. China is a large country with selenium deficiency, according to the "Atlas of Endemic Diseases and Environmental Factors of the People's Republic of China", 72% of China's areas are selenium deficiency, of which 30% are serious selenium deficiency areas, and 2/3 of the population has different degrees of insufficient selenium intake. Yu Ruomu, a famous nutrition expert, stressed when talking about the problem of selenium deficiency in China: We must pay attention to selenium supplementation like iodine supplementation!
Recommended intake: The Recommended Amount (RNI) of Adult Dietary Selenium of the Chinese Nutrition Society is 60 μg/day, and the maximum tolerable intake (UL) is 400 μg/day.
Main food sources: Seafood and animal offal are good food sources of selenium, such as caviar, sea cucumber, oysters, clams and pig kidneys. Selenium-rich yeast may also be supplemented as directed by a physician.
Copper (Cu): Element 29, subgroup 1 of the 4th cycle
Copper is an indispensable trace element in the human body. Adults generally contain 50 to 120mg of copper, copper can promote the absorption and transport of iron, maintain normal hematopoietic function, but also promote the health of bones, blood vessels and skin and maintain the integrity of the central nervous system. A normal diet can meet the body's need for copper, and it is generally not easy to appear deficient or excessive. Excess copper can cause acute and chronic poisoning, usually acute poisoning caused by drinking acidic beverages that have been in contact with copper containers or copper pipes for a long time, or taking large amounts of copper salts by mistake.
Recommended intake: The World Health Organization (WHO) recommends an average upper limit of 12 mg/day for adults and 10 mg/day for women. Combined with the dietary copper intake of Chinese residents, the recommended amount (RNI) of adult dietary copper of the Chinese Nutrition Society is 0.8mg/day, and the maximum tolerable intake (UL) is 8mg/day.
Main food sources: Shellfish foods contain high copper, such as oysters, oysters, etc., animal liver, kidneys and nuts, grain germs, beans and other copper content is also more abundant.
Chromium (Cr): Element 24, subgroup 6 of the 4th cycle
Chromium is one of the essential trace elements of the human body, first discovered and named by the French chemist Louis Vauquelin at the end of the 18th century, and plays a special role in the body's sugar metabolism and lipid metabolism. But in the following 100 years, this mineral element was considered a harmful element, even a carcinogen, and its application was limited to printing and dyeing, tanning, chemical and other industries. Until 1957, Schwarz and Mertz observed the role of chromium in glucose metabolism, proposed the glucose tolerance factor hypothesis, and gradually confirmed experimentally that Cr3+ is an active component of the glucose tolerance factor (GTF) in brewer's yeast. Trivalent chromium has a strengthening effect on insulin, which converts blood sugar into carbon dioxide and fat, and is an essential supplement for patients with high blood sugar and diabetes. In addition, chromium can also promote protein synthesis, growth and development, and has a certain preventive atherosclerosis effect.
Recommended intake: The current data is not enough to formulate UL, and the Chinese Nutrition Society recommends that the appropriate intake (AI) of adult dietary chromium be 30 μg/day.
Main food sources: Animal foods are rich in chromium in meat and seafood (oysters, sea cucumbers, squid, eels, etc.). Plant foods such as grains, legumes, nuts, black fungus, seaweed, etc. are rich in chromium. Chromium in brewer's yeast and animal liver is present in the form of biologically active glucose tolerance factors, which are highly absorbed and utilized.
Molybdenum (Mo): Element 42, subgroup 6 of the 5th cycle
The total content of molybdenum in the human body is about 9mg, and the molybdenum content is higher in the liver, kidneys and skin. Molybdenum is mainly involved in purine metabolism and uric acid excretion in the human body, when the human body's molybdenum intake is insufficient, purine metabolism is not timely will cause gout. According to the results of population epidemiological surveys, it is believed that low molybdenum may be related to the occurrence of esophageal cancer. Excessive molybdenum can also be harmful to the human body, mostly occurring in people in high molybdenum areas.
Recommended intake: The recommended amount (RNI) of molybdenum for adults of the Chinese Nutrition Society is 100 μg/day, and the maximum tolerable intake (UL) is 900 μg/day.
Main food sources: animal liver, kidney content is the most abundant, milk and dairy products, dried beans and cereals contain molybdenum is also more abundant.
Cobalt (Co): Element 27, paragroup 8 of the 4th cycle
The normal human body contains 1.1 to 1.5mg of cobalt, and the content of cobalt in the liver, kidneys and bones is high. Cobalt can promote the maturation of red blood cells and can also antagonize iodine deficiency, producing a thyroid-like function. China has not formulated a reference intake of cobalt, and active cobalt has the highest content in seafood such as crab meat, sardines, kelp, seaweed and squid; animal foods such as liver and kidneys are higher; vegetables, dairy products and various refined foods have low content.