Among the three carriages that regulate calcium, vitamin D is one of them (the other two are parathyroid hormone and calcitonin). There are two sources of vitamin D, one is synthesized in the body, that is, under the action of ultraviolet light, the skin can make the body’s cholesterol —- accurately 7-dehydrocholesterol, into vitamin D; the other is obtained from exogenous, that is, from food or drugs to supplement. Ordinary vitamin D is basically inactive and does not work as it should in the body; it has to be further activated by the liver and kidneys to work (this is the reason why some patients with liver and kidney impairment lack vitamin D). The role of vitamin D in the body is extensive. In addition to the regulation of calcium and phosphorus, it has an effect on other tissues and organs such as muscles, skin, brain and immune tissues. In the case of patients with osteoporosis, vitamin D helps to reduce the occurrence of falls due to its role in maintaining neuromuscular coordination, which of course reduces the chance of fractures. Thus, it can be seen that vitamin D has a wide range of roles in the human body, and if the body is deficient in vitamin D, it can lead to various diseases. For example, lack of vitamin D in childhood can easily lead to rickets; lack of vitamin D in adults can easily lead to osteochondrosis, etc. This is a classic study by medical predecessors and is based on the prevention of nutritional deficiency diseases. Because vitamin D has such a wide range of effects, it has an irreplaceable role in the prevention and treatment of osteoporosis. In the case of the elderly and postmenopausal women, a high-risk group, vitamin D deficiency is a major cause of primary osteoporosis due to a variety of reasons, such as poor synthesis and absorption in the body, degeneration of body functions, reduced liver and kidney function that affects vitamin D activation, and a number of other reasons. Therefore, adequate vitamin D supplementation, whether for normal people or osteoporosis patients, is necessary and beneficial. First, how much vitamin D supplementation is considered appropriate? Medical research shows that the human body vitamin D to achieve the ideal level (serum 25 (OH) D ≥ 32ng/ml, to achieve this level requires about 4000 IU of vitamin D), which in addition to natural foods, some nutrients, sunlight exposure, etc. the human body can get part of the vitamin D, the recommended amount of vitamin D for the elderly is recommended for 400 -800 U per day, taking into account the potential extra-skeletal role of vitamin D. The recommended amount of vitamin D can be moderately increased, taking into account the potential extra-skeletal effects of vitamin D. Foods rich in vitamin D: cod liver oil, sardines, herring, salmon, tuna, milk, dairy products, etc. Secondly, which people need vitamin D supplementation most? First, the rickets and adult osteomalacia patients mentioned earlier, most of these people are caused by vitamin D insufficiency, deficiency or vitamin D resistance; second, various causes of osteoporosis; third, hypoparathyroidism patients; fourth, patients with poor liver and kidney function, these people should be supplemented with activated vitamin D, such as alfacalcidol or osteotriol; fifth, various causes of low blood calcium . Of course, the reader to determine whether they have the above-mentioned disease point of difficulty, it is recommended that the necessary friends to go to the hospital to consult a specialist, to do some of the necessary tests. The above said so much, perhaps some people will say: vitamin D role so much, so good, then is not a lot of, a lot of supplementation. This is very wrong, all in the things have a “degree” problem, enough is good, more will be a problem, if you apply vitamin D in excess, will cause vitamin D toxicity and hypercalcemia, etc.. Therefore, if you need to apply vitamin D, it is best to do so under the guidance of a specialist to avoid unnecessary trouble. These two issues have described the role of calcium and vitamin D in the prevention and treatment of osteoporosis. Although simple calcium and vitamin D supplementation is not sufficient for satisfactory treatment of osteoporosis and osteoporotic fractures, it is indispensable and necessary in the treatment or prevention of osteoporosis. It is necessary because calcium cannot be synthesized in the body and vitamin D is not sufficiently synthesized in the body (especially in the elderly). Therefore, calcium and vitamin D supplementation is a necessary basis for the prevention and treatment of osteoporosis in middle-aged and elderly people.