Also known as vitamin PP, nixic acid is a coenzyme in the body for a variety of unwanted oxygen dehydrogenases. When deficient in nixic acid, mange can develop, mainly in the form of dermatitis, diarrhea and dementia. Dermatitis is often symmetrical and appears on exposed areas. Dementia is the result of neurodegeneration. Recently, nixic acid has been used clinically as a cholesterol-lowering drug. Nixic acid inhibits lipolysis in adipose tissue, thereby inhibiting the mobilization of free fatty acids, which can lead to a decrease in the synthesis of very low-density lipoproteins in the liver, thus having a cholesterol-lowering effect. Nixic acid is widely found in nature, and the liver can convert tryptophan into nixic acid, but the conversion rate is relatively low because tryptophan is an essential amino acid, and the human body mainly takes in nixic acid from food.