To prevent and treat osteoporosis in the elderly, the key is in calcium supplementation. Nowadays, bone strengthening powder, various calcium supplements and other calcium supplements are popular nationwide, and many elderly people are taking them. Obviously they have recognized the importance of calcium supplementation. However, some of them do not work well. It turns out that the body needs the assistance of vitamin D to absorb calcium. If there is a lack of vitamin D, despite the abundance of calcium in food, it still cannot be absorbed. To satisfy the body’s need for the vitamin requires the help of sunlight. There are two types of natural vitamin D, namely vitamin D2 and vitamin D3. The main form of vitamin D in the body is vitamin D1, and the body can synthesize about 200-400 international units of vitamin D3 per day. The vitamin D2 and D3 present in food can be absorbed by the intestine. In addition, ultraviolet light from sunlight can transform 7-dehydrocholesterol in the skin into vitamin D3, and the vitamin D we need daily is mainly obtained through sunlight exposure, except for a small portion supplied by food. Therefore, the body’s need for vitamin D can be fully met with adequate exposure to sunlight. Both vitamin D2 and vitamin D3 are not biologically active, but must be metabolized in the liver and kidneys to become physiologically active compounds, i.e. active vitamin D. Active vitamin D promotes the absorption of calcium by the intestinal mucosa. Therefore, in order to prevent senile osteoporosis, we need to supplement calcium, and in order to absorb calcium, we need to ensure that there is sufficient vitamin D in the body, and we need to do appropriate outdoor activities and receive sunlight. Exposure to sunlight for the elderly does not mean braving the heat and deliberately baking in the hot sun. Just be aware of the need to be outdoors regularly. Vitamin D deficiency can occur in the winter when the climate is cold and the elderly are less fit and often stay out of the house. When spring arrives, the wind and sunshine make it a good time to be outdoors and receive the sun’s rays for vitamin D supplementation. One thing to note is that ultraviolet light cannot pass through glass, so sunbathing through glass is not useful for increasing vitamin D in the body. In addition to the above measures, you should also exercise properly. The function of the skeletal system is to bear weight and movement, the more exercise, the stronger. In addition, take care not to drink alcohol. It has been reported that tobacco, coffee and Coca-Cola can cause vitamin D deficiency in the body and affect the absorption of calcium in the small intestine. Depending on the specific situation, osteoporosis prevention and treatment drugs can be applied to patients with osteoporosis. However, it should be especially noted that taking too much vitamin D can increase the blood calcium concentration, excessive deposition of calcium in the bones and calcification of the kidneys and other organs.