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==What is Vitamin E (α-Tocopherol)?==

==What is Vitamin E (α-Tocopherol)?==

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 Overview - Anatomy & Physiology|small intestine]]. Absorbed vitamin E is then incorporated into chylomicrons and released into the [[Lymphatic System Overview - Anatomy & Physiology|lymphatics]] for transport to the [[Liver - Anatomy & Physiology|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<ref name="Chow">Chow CK. Vitamin E. In Biochemical and physiological aspects of human nutrition. 2000 Philadelphia, PA: WB Saunders Company p.584-598.</ref>. The resultant α-tocopherol laden VLDLs transport α-tocopherol throughout the body. Vitamin E is primarily excreted through [[Bile acids|bile]] in faeces, though significant amounts of the metabolite α-tocopheric acid can also lost through urine<ref name="NRC">National Research Council (NRC). Vitamins. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.205-210.</ref>.  

Vitamin E is a category of '''[[Nutrition Glossary#Essential Nutrients|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 Overview - Anatomy & Physiology|small intestine]]. Absorbed vitamin E is then incorporated into chylomicrons and released into the [[Lymphatic System Overview - Anatomy & Physiology|lymphatics]] for transport to the [[Liver - Anatomy & Physiology|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<ref name="Chow">Chow CK. Vitamin E. In Biochemical and physiological aspects of human nutrition. 2000 Philadelphia, PA: WB Saunders Company p.584-598.</ref>. The resultant α-tocopherol laden VLDLs transport α-tocopherol throughout the body. Vitamin E is primarily excreted through [[Bile acids|bile]] in faeces, though significant amounts of the metabolite α-tocopheric acid can also lost through urine<ref name="NRC">National Research Council (NRC). Vitamins. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.205-210.</ref>.

==Why is it Important?==

==Why is it Important?==