Vitamin E

Vitamin E is a category of essential fat-soluble vitamins referred to as tocopherols. There are four stereoisomers of tocopherols found in nature (α, β, γ, and δ). Of these, α-tocopherol has the highest biological activity. Similar to other fat-soluble vitamins, vitamin E is incorporated into mixed micelles along with dietary fat and absorbed by diffusion across the mucosal surface of the small intestine. Absorbed vitamin E is then incorporated into chylomicrons and released into the lymphatics for transport to the liver, though some absorption into the portal circulation occurs as well. Within the liver selective α-tocopherol-binding proteins will incorporate α-tocopherol into very low density lipoproteins (VLDLs); α-tocopherol-binding proteins have only limiting binding of β-, γ-, or δ-isomers. The resultant α-tocopherol laden VLDLs transport α-tocopherol throughout the body. Vitamin E is primarily excreted through bile in faeces, though significant amounts of the metabolite α-tocopheric acid can also lost through urine. Vitamin E is an antioxidant that protects cellular membranes lipid peroxidation by free radicals.