Another reason why it is unusual is that its activation state is the most important hormone in the human body. This is the root cause of depression without it: there are fewer active hormones in the body.
Vitamin D is very important, the more the better. Excessive intake of vitamin D will lead to abnormally high calcium content in blood and calcium deposition in soft tissues (hoof tissues and blood vessels). The consequences of calcium deposition are very serious. If it develops, it will be joint calcification, ossification, bone destruction, arthritis, osteoarthritis and other symptoms, which will eventually affect all joints.
Vitamin D is the general name of four fat-soluble substances that maintain the balance of calcium and phosphorus in the body.
Include dehydrocholesterol, cholecalciferol, calcitriol and calcitriol.
Dehydrocholesterol (7- dehydrocholesterol) is a cholesterol derivative, which exists in human skin and can be converted into cholesterol calciferol (vitamin D3) by solar ultraviolet or artificial ultraviolet. The activation of cholecalciferol in vivo requires two metabolic processes. The first step is to convert it into calcitriol (25- hydroxyvitamin D or 25- hydroxycholecalciferol) in the liver. The second step is to convert it into calcitriol (or osteocalcin 1, 25- dihydroxyvitamin d, calcitriol) in the liver.
Calcitriol is an activated form of vitamin D, which enables vitamin D to play its main physiological functions. The amount of calcitriol in the body is strictly controlled in the body balance system, and it is produced in the kidney according to the needs of the body. The main control factors are the existing level of calcitriol in the body and the levels of parathyroid hormone, calcium and phosphorus in the blood.
Vitamin D3 and vitamin D2 can be supplemented from food. Vitamin D3 mainly comes from animals and is the main source of vitamin D supplementation for human body. Plants also contain a small amount of provitamin D, called ergosterol, which can be converted into vitamin D2, similar to vitamin D3, and can also be further converted into active vitamin D in liver and kidney.
Vitamin D2 and vitamin D3 are absorbed in the small intestine because they are fat-soluble and transported to the liver with chylomicrons.
The most typical function of vitamin D is to regulate the metabolic balance of calcium and phosphorus in the body. By guiding and controlling the metabolic balance of calcium and phosphorus, vitamin D plays an important role in the muscles and nerves of the body and plays an important role in the process of bone formation and mineralization.
The function of calcitriol is similar to that of cholesterol hormone. In order to exert its biological function, calcitriol binds to a special receptor VDR, which is located in the nucleus of the target cell. The calcitriol receptor (VDR) binds to DNA together with the RXR receptor activated by vitamin A, so it acts on a series of tissue genes. These tissues include bones, kidneys and small intestine, as well as immune system, endocrine system, skin and tumor cells, which are involved in maintaining calcium balance in the body.
Calcineol and vitamin D receptors in body organs and tissues are not directly involved in calcium metabolism, indicating that vitamin D has other functions. Some studies have shown that the concentration of calcitriol is significantly higher than that of calcitriol at the circulating level. So it is possible that some special cells can locally produce calcitriol. From this point of view, some studies have also shown that activated macrophages in white blood cells can produce calcitriol, which also affects the reproduction, differentiation and immune function of white blood cells.
Some medical experiments have also found calcitriol in tumor cells. Calcitriol can promote the growth of tumor cells at low concentration, inhibit the proliferation of tumor cells and promote apoptosis at high concentration.
However, whether vitamin D affects the immune system and the risk of human tumors is still controversial.
Besides regulating the function of DNA, calcitol also has some non-genomic functions.
In intestinal cells, calcitriol absorbs cell membrane calcium transporters located in small cavities on the cell surface, leading to the rapid growth of calcium.
In some cells, calcitriol acts through cell surface receptors instead of calcitriol receptors in the nucleus, which leads to rapid intracellular calcium exchange channels, thus triggering a series of intracellular hierarchical superposition activity signal reactions. This effect is considered to inhibit cell proliferation and promote cell differentiation.
Insufficient vitamin D in the body will lead to the increase of parathyroid level and the disorder of calcium and phosphorus balance system in the body.
Some children lack vitamin D, which may cause some symptoms such as fidgeting, fidgeting, sweating and loss of appetite. Long-term lack of vitamin D in children can lead to rickets, which is characterized by stunted growth and abnormal bones. In the period of rapid development, children are prone to vitamin D deficiency due to the need of accelerated bone growth.
Rickets is the result of long-term lack of essential calcium and phosphorus in bones. Some serious symptoms may cause bending of arms and legs, and some may also lead to the closure of baby's crown and insufficient enamel mineralization.
In some serious cases, the low calcium level in the blood will affect the nervous system and also cause epilepsy.
Vitamin D deficiency can also harm adults. With the growth of age, the bones of adults will gradually lose calcium and phosphorus, leading to osteochondrosis. The initial symptom of rickets is bone and muscle pain, and then it develops into muscle weakness and muscle spasm, which increases the defense line of infection. Severe vitamin D deficiency can lead to brittle bone disease. Vitamin D deficiency is also related to osteoporosis that the elderly often suffer from, which increases the risk of fracture and muscle weakness.
Acute vitamin D poisoning can lead to loss of appetite, weight loss, increased urine output and arrhythmia. Other serious results include the increase of calcium concentration in blood, which will lead to urinary calculi and calcification of blood vessels and tissues, causing damage to the heart, blood vessels and kidneys.
Excessive exposure to sunlight will not lead to vitamin D poisoning, because the heat of human skin is thought to degrade D3 (pre-vitamin D3.
Long-term intake of excessive vitamin D is considered to increase health risks, increase the risk of some tumors, cardiovascular diseases, and the risk of falls and fractures in the elderly. These symptoms are due to the high level of calcium circulation in the body, which will lead to bone calcium loss and promote excessive urinary calcium loss. Symptoms of high calcium in the body include excessive urine, excessive thirst, vomiting, loss of appetite, dehydration, listlessness, constipation, hypertension, muscle spasm and epilepsy.
In the past 20 years, people's understanding of vitamin D has changed from being mainly related to rickets and calcium metabolism to being a cure for all diseases. American Time magazine even listed vitamin D as 10 when evaluating the medical breakthrough in 2007.
It is generally believed that vitamin D deficiency is related to osteoporosis, hearing loss, obesity, heart disease, cancer, muscle pain, asthma and other diseases. Some websites claim that sleep disorders are caused by lack of vitamin D, while others say that vitamin D can make people smarter. It is said that vitamin D is related to 100 diseases.
However, some recent empirical studies also show that the effective population of vitamin D supplements seems to be limited. For example, it is effective for some children, pregnant women or patients with chronic kidney disease to take it for a long time; However, vitamin D supplementation has no special effect on some adults and the elderly. Others retort that even though vitamin D itself may have no obvious effect on the elderly, the combined effect of vitamin D and calcium can reduce the risk of fracture in the elderly.
Generally speaking, even if not everyone needs vitamin D supplementation, children, people over 70 years old, people with dark skin and people who seldom bask in the sun need food to supplement vitamin D. Therefore, people with white skin can at least be proud, because it takes 15 minutes to make their skin synthesize vitamin D every day, so people with dark skin need 30 minutes or 40 minutes to achieve the same effect.
Vitamin d is rarely found in food. The main source is cod liver oil, which is why cod liver oil has been the main force to prevent and treat healthy D deficiency for a long time.
Saltwater fish sardines, herring, salmon and mackerel are also rich in vitamin D. Eggs, meat, milk and cream also contain a small amount of vitamin D.
Plants basically do not contain vitamin D, and fruits and nuts basically do not contain vitamin D.
1, developing children or teenagers need to supplement cod liver oil, or eat some fish rich in vitamin D regularly: sardines, salmon and mackerel.
Both young people and old people should eat proper meat and foods rich in cholesterol. Cholesterol can be converted into dehydrocholesterol under certain conditions, which creates reserve conditions for human body to make vitamin D, although there is no information about the chemical change mechanism of fatty acids neutralizing cholesterol in the body and 7- dehydrocholesterol in the skin. However, it is inferred that the relationship between dehydrocholesterol and cholesterol is a chemical reaction, so the body needs to store some cholesterol.
3. Both young and old should consider having 15-30 minutes of light time at a time, or sunbathing. The skin in the human body can convert dehydrocholesterol into calcium cholesterol, and then synthesize calcitriol in the liver and calcitriol in the kidney, providing the body with living calcitriol hormone and making the body full of vitality.
4, don't be superstitious and exaggerate the role of vitamin D, and make up health care products containing vitamin D. Excessive vitamin D and overweight will lead to vitamin D poisoning. On the contrary, it will affect health and cause diseases.