Cholesterol is the most abundant steroid compound in the body, and as a component of cellular biofilms and a precursor to steroid hormones, bile acids and vitamin D, it is important for most tissues to ensure its supply and maintain its metabolic balance. Cholesterol is found in a wide range of tissues throughout the body, with about 1/4 of it in brain and nerve tissue, accounting for about 2% of the total weight of brain tissue, and more in internal organs such as liver, kidneys, intestines and adipose skin tissue. Cholesterol can be divided into good cholesterol, in the form of HDL, and bad cholesterol, in the form of LDL, which indicates an increased risk of coronary heart disease and is often referred to as bad cholesterol. HDL has a protective effect on blood vessels and is often referred to as good cholesterol.