The main physiological functions of vitamin D: 1. Improve the body’s absorption of calcium and phosphorus; 2. Promote growth and bone calcification, and promote healthy teeth; 3. Increase the absorption of phosphorus through the intestinal wall and pass through the kidneys The tubules increase the reabsorption of phosphorus; 4. Prevent the loss of amino acids through the kidneys. 2. Effects of lack or excess of vitamin D on health. Lack of vitamin D in the human body can cause rickets, tetany, and rickets. Long-term intake of too much vitamin D (5000IU/day) will cause hypercalcemia and hypercalciuria. It is characterized by loss of appetite, excessive thirst, nausea, vomiting, irritability, weakness, alternating occurrence of constipation and diarrhea, and in severe cases, death due to renal calcification, calcification of the heart and aorta. 3. People who need vitamin supplements 1. People who live in cities, especially those in smoke-polluted areas, should take more vitamin D; 2. People who work at night or cannot get enough sunlight due to clothing or lifestyle People who are pregnant should pay special attention to increasing their intake of vitamin D in their diet; 3. If you are taking anti-spasmodic drugs, you must increase your intake of vitamin D; 4. Children who drink milk without vitamin D must increase their intake of vitamin D. Amount; 5. People with darker skin and living in northern climate areas need more vitamin D. Vitamin D, also called calciferol, has an anti-rickets effect. Vitamin D deficiency can occur when there is insufficient vitamin D intake, insufficient sunlight exposure, or malabsorption. The main function of vitamin D is to regulate calcium metabolism, promote calcium absorption and bone tissue formation. Therefore, when vitamin D is deficient, children may suffer from the same rickets as calcium deficiency, with occipital baldness, square skull, chicken breast, and "O" or "X" shaped legs. Adults present with rickets, leading to bone hyperplasia and osteoporosis. 4. Sources of vitamin D: Vitamin D is rich in fatty marine fish, fish eggs, liver, whole milk, egg yolks, cod liver oil, butter, and cream. Sunlight can convert 7-dehydrocholesterol existing under the skin into vitamin D3, so sun exposure is the cheapest way to obtain vitamin D