For a period of time, vitamin D was said to be a miraculous elixir. A century ago, people began using vitamin D to treat rickets. Rickets is a childhood disease that can lead to fragile and deformed bones. By the beginning of the 21st century, some researchers believed that the low level of vitamin D in the human body might be related to cancer, cardiovascular diseases, dementia, depression, diabetes, autoimmune diseases, fractures, respiratory diseases and Parkinson's disease, after collecting a large number of research data. Some writings and reports suggest that by increasing the level of this vitamin in the body, such as sunbathing or taking vitamin D supplements, any disease that troubles humans can be cured. During this period, at least two books titled "Vitamin D Therapy" were published. In the titles of some books and news reports related to vitamin D, words such as "revolution" and "miracle" may also appear. Many people are becoming increasingly concerned about insufficient intake of vitamins. In an episode of Good Morning America, a journalist named Diana Sawyer claimed that up to 100 million Americans lack vitamin D. The guest on the show, Dr. Oz, told the audience that a simple blood test can be used to determine one's own level of vitamin D. He said that sunbathing is the best way to obtain this vitamin. But if it's still not enough, he suggests taking fish liver oil or vitamin D supplements. Joan Manson, an endocrinologist and epidemiologist at Harvard Medical School in the United States, is the lead researcher in some large-scale vitamin D related studies. She said that with the encouragement of many celebrities and vitamin production companies, people have begun to believe that vitamin D may be a "miracle drug". The sales of supplements containing vitamin D have skyrocketed, and the number of people testing vitamin D levels has also increased significantly. But the fact is not so. Although thousands of studies have linked low levels of vitamin D to various diseases, when scientists try to use vitamin D to prevent or treat these diseases, this "magical" supplement is a failure. The idea that if people increase their levels of vitamin D in their bodies, their lives will become better seems like a fantasy. At the same time, the claim that people generally lack vitamin D has become untenable. It has been proven that the widespread lack of vitamin D was initially sparked by a misunderstanding. A sampling survey of the national population in the United States shows that the vast majority of the human body has sufficient vitamin D. Undoubtedly, vitamin D plays an important role in maintaining human health. It helps the human body absorb and store calcium and phosphorus, both of which are crucial for bone growth. However, except for minority groups (such as breastfed infants and those with special illnesses), most people may not need to take vitamin D supplements. Vitamin D was discovered and quickly pushed onto the altar, but ultimately returned to its original form, indicating that the path of scientific exploration can sometimes be full of twists and turns. This is also a cautionary story, reminding people not to arrogantly understand scientific research achievements. Most importantly, it demonstrates the trait of scientific self correction and how knowledge gradually improves over time. Sunshine and obtaining vitamin D in humans