ABSTRACT
Vitamin E, discovered in 1922, consists of eight structurally related antioxidant molecules (α-, β-, γ-, and δ-tocopherols and α-, β-, γ-, and δ-tocotrienols) produced by plants or synthetically (Niki and Traber 2012). Of the eight stereoisomeric forms, it is the four 2R α-tocopherol forms (α-and γ-tocopherol) maintained in human plasma that are considered biologically important (Traber 2013). Because of the specificity of α-tocopherol transfer protein (α-TPP) in the liver (Reboul et al. 2009), the major form in circulation across all forms of lipoprotein fractions is α-tocopherol despite the predominance of γ-tocopherol as a US dietary source (Ford et al. 2006). Thus, α-tocopherol is the most abundant form in tissues and the only form retained at high levels in humans (Cohn 1997). Unlike other fat-soluble vitamins, for example, vitamins A and D, α-tocopherol does not accumulate in the liver or extra-hepatic tissues (IOM 2000). Using isotopically labeled α-tocopherol, blood sampling and complete urinary and fecal collections in six men and six women, (Chuang et al. 2011) measured apparent absorption of 79% with feces being the major route of elimination (23%) followed by urine (4%). The half-life of 14C-tracer, measured over 70 days (d),
10.1 Introduction .................................................................................................. 239 10.2 Deficiency Requirements ..............................................................................240 10.3 Status Assessment .........................................................................................240 10.4 Genetic Factors ............................................................................................. 241 10.5 Optimal Vitamin E Status ............................................................................242 10.6 Vitamin E Status and Non-Communicable Diseases ................................... 243
10.6.1 Cancer ............................................................................................... 243 10.6.2 Brain Health, Cognition, and Depression .........................................244 10.6.3 Liver Function ...................................................................................244 10.6.4 Metabolic Syndrome, Diabetes, and Cardiovascular Health ............245 10.6.5 Urinary and Reproductive Health .....................................................246
