How to classify vitamins

For an enzyme to be active, it must include a coenzyme. Many vitamins are known to be coenzymes or constituent molecules of coenzymes. Therefore, vitamins are important substances in maintaining and regulating normal metabolism in the body. It can be believed that vitamins exist in human tissues in the form of "biologically active substances".

The vitamin content in food is small and the human body needs not much, but it is an indispensable substance. A lack of vitamins in the diet will cause metabolic disorders in the body, resulting in vitamin deficiency. For example, lack of vitamin A can lead to night blindness, dry eye disease and dry skin; lack of vitamin D can lead to rickets; lack of vitamin B1 can lead to beriberi; lack of vitamin B2 can lead to cheilitis, angular stomatitis, glossitis and scrotum inflammation; lack of PP can lead to mangy disease; lack of vitamin B12 can lead to pernicious anemia; lack of vitamin C can lead to scurvy.

Vitamins are a huge family. There are dozens of vitamins currently known, which can be roughly divided into two categories: fat-soluble and water-soluble. See the table below for details. Some substances are similar in chemical structure to certain vitamins and can be converted into vitamins through simple metabolic reactions. Such substances are called provitamins. For example, beta-carotene can be converted into vitamin A; 7-dehydrocholesterol can be converted into vitamin D3; However, tryptophan, which requires many complex metabolic reactions to become niacin, cannot be called provitamins. After water-soluble vitamins are absorbed from the intestine, they are circulated into the tissues needed by the body. Most of the excess is excreted in urine and little is stored in the body. Most fat-soluble vitamins are absorbed by bile salts and travel through the lymphatic system to