1, the synthesis of human body itself
Vitamin D is converted from the corresponding vitamin D by ultraviolet irradiation. The epidermis and skin tissues of most higher animals contain 7- dehydrocholesterol, which can be converted into vitamin D3 by photochemical reaction under sunlight or ultraviolet radiation. Vitamin D is mainly D3 and D2, and vitamin D3 is made from 7- dehydrocholesterol under human skin by ultraviolet radiation. D2 is made from ergosterol contained in plants or yeast by ultraviolet irradiation.
90% of vitamin D in human body comes from sunlight, and the other 65,438+00% comes from food, so you should always bask in the sun to ensure enough ultraviolet radiation. In order to avoid strong sunlight, it is recommended to bask in the sun before 10 in the morning or after 3 pm, and expose the head, face, upper limbs and lower limbs (the exposed body surface area is greater than15%) for 20 to 30 minutes.
Step 2 get food
Vitamin D3 mainly exists in marine fish, animal liver, egg yolk and lean meat, skim milk, cod liver oil, cheese, nuts and seafood, among which the fat content in marine fish, animal liver, egg yolk and cream is relatively high, and the content in cod liver oil is relatively high.
3. Supplementary addition
Vitamin D in food is very limited. The Nutrition Society of China suggested that the age of 0-64 (including pregnant women and lactating mothers) should be supplemented with 400IU per day, and the age of 65 and above should be supplemented with 600IU per day. By strengthening food, dietary supplements, drugs and other supplements.
The functions of vitamin D are: regulating calcium and phosphorus metabolism, promoting bone growth, regulating cell growth and differentiation, and regulating immune function.
1, regulating calcium and phosphorus metabolism
The total effect of active vitamin D on calcium and phosphorus metabolism is to increase blood calcium and phosphorus and make plasma calcium and phosphorus level reach saturation level, which is beneficial to calcium and phosphorus deposition on bone tissue in the form of bone salt and promote calcification of bone tissue.
2. Promote bone growth
Vitamin D3 promotes bone calcification by increasing the absorption of calcium and phosphorus in the small intestine. Even if intestinal absorption does not increase, it can still promote bone salt deposition, which may be the result that vitamin D3 makes Ca2+ enter bone tissue through osteoblast cell membrane.
3. Regulate cell growth and differentiation
1 and 25- dihydroxyvitamin D3 can regulate the growth and differentiation of leukemia cells, tumor cells and skin cells.
4. Adjust immune function
Vitamin D has immunomodulatory effect and is a good selective immunomodulator. It has certain curative effect on preventing and treating autoimmune encephalomyelitis, rheumatoid arthritis, multiple sclerosis, type I diabetes and inflammatory bowel disease.
Extended data
A recent study by American scholars found that taking vitamin D supplements can help reduce the death risk of cancer patients 13%.
According to reports, the study was jointly conducted by Michigan State University and Hurley Medical Center in Michigan. The researchers collected data of 79,000 people with an average age of 68 and followed them for at least three years.
It was found that taking vitamin D supplement can reduce the risk of cancer, but it can reduce the risk of death after cancer by about 13%. The report failed to explain how vitamin D can help reduce mortality, but researchers said that vitamin D can help improve the immune system and prevent tumor cells from growing.
People's Health Network-Vitamin D has more effects and less sunshine, or needs to be supplemented.
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