Here is my personal review of some of the products that are on the market and the information that I believe is relevant to most people.
You may have read that the recommended daily allowance of vitamin D is 600 IU. That means that if your vitamin D level is 25,000 IU, you are supposed to take 600 IU of vitamin D every day. Many vitamin D supplements are not very good or contain little or no vitamin D, but most people don't take supplements because they think that they are taking a good supply of vitamin D. But when you eat foods high in vitamin D, you are not getting enough of the vitamin. So, many people eat foods that contain vitamin D, but the amount that they need is not enough to supply their needs. If you take too much vitamin D, you can get sick and die from getting too much exposure to sunlight and vitamin D. Vitamin D is important for bone health. It regulates the activity of genes in the body and the production of collagen and connective tissue. It is also important for immune function and for regulating the release of hormones. Some people may have high vitamin D and a low body temperature, but others may have low vitamin D and high body temperature.