It was not until the beginning of the 20th century that people realized that in our food, in addition to the known sugars, lipids and protein, there is also a substance with little content but very important functions-vitamin, which is an essential nutrient to maintain human life. Vitamins, also known as vitamins, are a kind of organic substances necessary to maintain human life activities and important active substances to maintain human health. The content of vitamins in the body is very small, but it plays an important role in the process of human growth, metabolism and development.
19 12 marks the beginning of the development of vitamins, and Polish chemist Fink put forward "vitamins". In the past 100 years, countless scientists have devoted themselves to research and made great achievements in this field. The human body is like a huge and complex chemical plant, which constantly carries out various biochemical reactions. These biochemical reactions are all completed under the catalysis of enzymes. In order to complete the catalytic function, enzymes must be assisted by other substances, which are called "coenzymes". Most vitamins themselves are such coenzyme or an important component of coenzyme. Therefore, it is generally believed that vitamins are a kind of low molecular weight compounds necessary to maintain the normal metabolism and function of the body, and they are one of the six nutritional elements of the human body (sugar, lipid, protein, water, inorganic salts and vitamins). Most of them must be taken from food, and only a few vitamins can be produced in the body or by intestinal bacteria. Up to now, there are 14 kinds of vitamins recognized all over the world, some of which are soluble in fat, while others are soluble in water but not in fat. According to this property, this 14 vitamin can be divided into fat-soluble vitamin and water-soluble vitamin.
Fat-soluble vitamins:
Vitamin a, vitamin d, vitamin e, vitamin K.
Water-soluble vitamins (including B vitamins and vitamin C):
B vitamins: vitamins, vitamins, pantothenic acid, nicotinic acid, vitamins, vitamins, biotin, folic acid, vitamins.
Vitamin food source
The earliest discovery of vitamin was in 1922, and Cramer separated vitamin A from vitamin D. ..
Vitamin A exists in animal fat. The main natural foods with vitamin A activity are dairy products, eggs, animal livers and colored vegetables, such as red peppers, carrots, spinach and alfalfa. Carotenoids in plants can be converted into vitamin A by the small intestine wall, so they are considered as precursors of vitamin A, which has physiological activity. Usually, the content of carotenoids in colored plants is higher than that in colorless plants.
Vitamin A can synthesize rhodopsin in human body, which exists in the cells of our retina and is related to vision in low light environment. When vitamin A is deficient, the synthesis of rhodopsin will slow down, or even cannot be synthesized, so that it can't be seen clearly at dusk, which is called night blindness. China ancient folk treatment of night blindness, as long as the animal's liver is boiled with clear water, and even the liver is eaten with soup, the effect is very good. Or eat more green vegetables, which is equally effective.
Vitamin A is also an essential substance to maintain the health of human epithelial tissue. When lacking, the skin and respiratory mucosa will become dry and keratinized, the ability to resist microorganisms will be reduced, and diseases such as colds and bronchitis will be easily infected. The epithelium of lacrimal gland will also be keratinized, and the secretion of tears will be reduced, resulting in dry eyes.
Normal adults need 2500 international units of vitamin A every day. If this standard is exceeded, vitamin A will accumulate in the body and cause poisoning symptoms. Therefore, you can't blindly supplement too much vitamin A.
illuminate
Britain was the first country to carry out the industrial revolution. 17- 18 century, tall buildings in major cities have stood in the air, and factory chimneys are row upon row, spewing smoke. Sometimes, even the whole "foggy city" has become a "smoky city". What followed was a strange disease that was rarely seen before, and most of them were children. Their bodies are deformed, their heads are square and big, their breasts are protruding like chickens, their legs are bent and they walk crooked. This is what medicine calls "rickets". Rickets is a systemic disease. In severe cases, convulsions, pneumonia, hepatosplenomegaly, diarrhea, anemia and other symptoms may occur, and even death may occur. 1870,13 children in London suffered from severe rickets, and 40% children in Manchester were sick. By 1920, the British government found that 30% children in primary schools still suffer from rickets to varying degrees. In sunny Egypt, rickets rarely occurs. In view of this situation, some people think that the cause of rickets lies in insufficient light. Later, it was found that if the sick puppy was fed a spoonful of cod liver oil every day, the puppy would recover from rickets quickly even if it was not in the sun, as did other animal experiments. This shows that cod liver oil and sunshine have the same therapeutic ability, and rickets may be caused by lack of some nutrition.
In fact, whether it is light or nutritional supplement, there is an important substance at work, that is, vitamin D. The most vitamin D content is fish liver and fish body fat. Ergosterol in plants and 7- dehydrocholesterol in animals can be converted into vitamin D by ultraviolet irradiation. Vitamins and vitamins are the two most important vitamins D in 10. Edible cod liver oil can directly supplement vitamin D, and in the sun, the original 7- dehydrocholesterol in the human body can be synthesized into vitamin D under ultraviolet radiation. According to the determination, the vitamin synthesized by adults in the sun in one day is equivalent to oral vitamin D 10000 international units, which is more than 100 times of the daily physiological requirement. The above two methods can effectively prevent and treat rickets.
Vitamin D can promote the absorption of calcium and phosphorus in intestine, increase the concentration of calcium and phosphorus in blood, and promote the calcification and growth of bone tissue. Lack of vitamin D in adults can cause osteomalacia, and lack of vitamin D in children can cause rickets. The daily requirement of adults is 100 international units. Taking a large amount of vitamin D for a long time can also lead to poisoning.
In the same year that vitamin A and vitamin D- 1922 were separated in Colam, Evans and others discovered another fat-soluble vitamin-vitamin E, which is a nutrient that many vertebrates must take from food.
1929, Danish doctor Damme used chicken as the material for biochemical research. He happened to find that chickens fed with his own special feed had bleeding under the skin and muscles, which was related to the long coagulation time. In the next five years, he tried countless times, but he couldn't find the cause of bleeding. It was not until the summer of 1934 that he changed the formula of feed to make all sick chickens recover. Further research found that natural green plants can restore this hemorrhagic disease.
Prolonged clotting time leads to bleeding, which is also common in humans. Skin trauma usually bleeds, but ordinary small wounds will automatically stop bleeding in a short time. However, some people will bleed because of a small wound. This phenomenon has a long history. In ancient medical books in China and Egypt, there are records of maternal death due to bleeding during childbirth. In ancient Europe, when doctors extracted teeth from patients, they often died of bleeding.
At the earliest time, people found that this bleeding symptom was related to the lack of certain food ingredients. Through research, people extracted a new vitamin-vitamin K from alfalfa and rotten fish. The structure of vitamin K from two different sources is slightly different. Vitamins extracted from green leafy plants and obtained by bacterial decay are vitamins, but their main structure is a naphthoquinone ring, that is, 2- methyl-1, 4- naphthoquinone, which is artificially synthesized.
alfalfa
Because human intestinal bacteria can synthesize vitamin K, the demand for vitamin K by adults is very small, and there are few cases of vitamin K deficiency. Vitamin K deficiency will only appear if you take a lot of antibiotics for a long time. Because of the low content of vitamin K in breast milk, newborns and premature infants are more likely to suffer from vitamin K deficiency. Generally, green plants are rich in vitamin K, which provides a sufficient source for human beings.
Blood coagulation is a complex physiological process, which is influenced by dozens of coagulation factors, and vitamin K is related to the synthesis of coagulation factors II, VII, IX and X in the liver. Lack of vitamin K will prolong the time of blood coagulation. According to this truth, American doctor Nailke uses the length of human coagulation time to judge whether vitamin K is deficient and the degree of deficiency. Until now, this method is still widely used in hospitals.