1979, the world health organization announced 14 kinds of essential trace elements for human body: iron (Fe), zinc (Zn), Copper (Cu), chromium (Cr), manganese (Mn), cobalt (co), fluorine (f), iodine (I) and selenium. In recent years, people have found and confirmed that lithium (Li), silicon (Si), bromine (Br) and boron (B) are beneficial to human health. The elements that are obviously harmful to human health are mainly some highly toxic elements, such As Be, Cd, Hg, Pb, As, Te, Sb and Te.
Although trace elements only account for about 0.05% of the total weight of human body, their nutritional functions and metabolism are of great significance. Regarding the relationship between trace elements and human health, Dr. H.A. Schroeder (1965), a famous American medical scientist, once had such an incisive exposition: "For life, trace elements are more important than vitamins, because they cannot be synthesized like vitamins, but must exist in the environment in a narrow concentration range ..."
There is a quantitative physiological dose range of biological trace elements in the body, and when the intake is insufficient, the symptoms of deficiency will appear; When the intake is too high, the symptoms of poisoning reappear. It has an optimal safe intake, and different elements have different suitable ranges. Therefore, in the national standard of Drinking Natural Mineral Water, in addition to the nine boundary indicators as the characteristic indicators of mineral water, there are also 18 limit indicators. Even the trace elements beneficial to human body should not exceed the allowable content, which is harmful to health and even poisoning. With the deepening of life science research, people have a deeper understanding of the value of trace elements in life. The physiological functions of trace elements include the following aspects:
(1) Trace elements play a specific activating role in the enzyme system: some trace elements are important components of various enzymes in the body. Enzymes are large and extremely complex protein structures, which can accelerate biochemical reactions. Most known enzymes contain one or several metal atoms. When trace metals are lost in the enzyme molecule, the activity of the enzyme will be lost or reduced. When these trace metals are recovered, the enzyme activity will return to normal.
(2) Trace elements help hormones in the body to play a role, that is, participate in hormone action: hormones are chemicals secreted into the blood stream by endocrine glands in the human body. Hormones can regulate important physiological functions of human body. Because hormones only need to interact with several key positions on the cell surface or inside the cell, and trace elements can make hormones play such a role. For example, iodine plays such a role in thyroxine.
(3) Delivering common elements to the whole body: Trace element iron is an important component of hemoglobin of red blood cells, and hemoglobin brings oxygen to tissues and cells. If there is iron deficiency, hemoglobin cannot be synthesized, oxygen cannot be transported, and tissues and cells cannot carry out normal metabolism.
(4) Balance human physiological functions: Trace elements can regulate osmotic pressure, ion balance and acid-base in body fluids, and maintain normal physiological functions of human body.
(5) Heredity: Trace elements are related to the function of nucleic acid. Nucleic acid is the carrier of genetic information, and there are quite a few trace elements (chromium, iron, zinc, copper, manganese, nickel, etc. ) in nucleic acid. Animal experiments show that these elements can affect the metabolism of nucleic acids, so trace elements may play a role in heredity.
(6) Participate in the structure of vitamins: Some trace elements are active components of vitamins, such as cobalt in vitamin B 12. Without cobalt, vitamin B 12 cannot be synthesized.
In addition, it should be pointed out that for the function and significance of trace elements in human body, we should not only pay attention to the specific properties of an element in isolation, but also pay attention to the interaction and complex relationship between various trace elements. At present, the interaction of various elements in the body is clearly understood as antagonism and synergy.
The antagonistic effect of elements in the body is mainly manifested in affecting absorption and substitution. For example, cadmium is very toxic, and zinc and cadmium have antagonistic effects. Animal experiments have proved that animals ingesting a certain amount of cadmium can cause hypertension, but if zinc exists, it can antagonize the toxic effect of cadmium and hinder the formation of hypertension. In addition, selenium has antagonistic effects on elements such as mercury, arsenic and cadmium. Selenium can significantly inhibit and weaken the toxicity of mercury compounds, offset or prevent the toxicity of arsenic and cadmium, including hypertension caused by cadmium. Copper, zinc and cadmium also showed antagonistic effects. Animal experiments show that when food contains a lot of zinc, the ability of animals to absorb copper is obviously reduced, and the existence of cadmium can interfere with the absorption of copper by intestinal tract. Another manifestation of antagonism is substitution, such as arsenic replacing phosphorus, tungsten replacing copper, mercury replacing zinc, mercury cadmium replacing copper, silver gold replacing copper and so on. Obviously, when non-essential or harmful trace elements replace or replace essential trace elements, it will inevitably have adverse effects on human metabolism, endanger health and even cause pathological changes. So the opposition between elements is worthy of attention.
The synergistic effect between elements is mainly manifested in mutual promotion. For example, copper-containing hemoglobin is a direct molecular bridge between iron and copper. Without copper, iron can't enter hemoglobin molecules in biosynthesis mechanism. Anemia can occur in both humans and animals when iron is sufficient and copper is insufficient. Manganese and iron can also interact. Animal experiments show that the absorption of manganese in gastrointestinal tract is obviously reduced when iron is deficient in feed. For another example, copper is also closely related to calcium, vanadium, iron, copper, phosphorus, sulfur and other elements, which seem to directly or indirectly affect the physiological functions of copper.
To sum up, the significance of trace elements to human health is self-evident.
Answer supplement
All kinds of foods are rich in trace elements, so we can meet our human needs by paying attention to a reasonable diet. Efforts should be made to diversify the diet structure, and coarse grains should be properly matched with coarse grains. In addition, for children, they must not be partial eclipse, and they must not cause excessive nutrients, so they must maintain a nutritional balance.
The contents of different trace elements in different foods are more or less. The following is a reference table of some foods with high trace elements content.
Foods high in trace elements:
Iron egg yolk, pork liver, kelp, fungus, spinach, laver, celery, soybean, mung bean, eggplant, tomato, sugarcane, wax gourd, apple, etc.
The contents of liver, kidney, fish, shrimp and clam of copper animals are high, and there are also some contents in fruit juice and brown sugar.
The zinc content in fish, meat, animal liver and kidney, beans and wheat is high.
Fluorine wheat, rye flour, fruit, tea, meat, vegetables, tomatoes, potatoes, carp, beef, etc.
Selenium herring, sardines, kidneys, liver, meat, eggs, sesame, malt, garlic, beer yeast, etc.
Iodized kelp, laver, marine fish and sea salt are rich in content.
Cobalt green plants are rich and diverse sources of cobalt in human food.