Collagen is one of the protein needed by human metabolism, which can be taken for a long time. Appropriate collagen supplementation can make the skin elastic and tough, and keep it soft and delicate. But there is a limit to everything. Before the age of twenty-five, the human body will still synthesize collagen. If you are under twenty-five, you can eat more foods containing collagen, such as pig's trotters, animal tendons and skin. If you feel that there is something wrong with your skin, you must supplement collagen directly. You can also take health care products in a short time.