Vitamin E natural compounds AlphaTocopherol a k a

Vitamin E natural compounds

Alpha-Tocopherol a. k. a. Vitamin E

Vitamin E • Vitamin E is a famil of a-, b-, g-, d- tocopherols and corresponding tocotrienols izomers. • They are formed from chroman ring and hydrofobic fytyl side chain. • The highest biological activity has a-tokoferol.

Vitamin E as an antioxidant R· + TOH ¾® RH + TO·

Vitamin E as antioxidant • Stops free radical reactions (peroxyl radicals ROO , oxygen radicals HO , lipoperoxid radicals LOO ). Chroman ring with OH group → uptake radicals.

Vitamin E Function Oxidative damage Free radicals Quenched radical

Absorption and Transport • • Dependent on ability to absorb fat Absorbed into lymphatic system Component of chylomicrons Alpha-tocopherol is major tocopherol in plasma • Positive association between serum lipid and tocopherol levels • Normal range is 0. 5 -1. 6 mg/dl

E-Facts • Plays a role in immune function, DNA repair, other metabolic processes, and in protecting other antioxidants • U. S. RDA : 15 mg (22. 5 IU) per day • Typical Western diet provides 14 mg (21 IU) of Vit E • Upper allowable intake (prior to Meta-Analysis): 1000 mg (1500 IU)

2005 Annals of Int Med: “Meta-Analysis: High-Dosage Vitamin E Supplementation May Increase All-Cause Mortality” • Three previous meta-analyses that did not consider the dose-dependent effect of vitamin E concluded that vitamin E was neither beneficial nor harmful. • New Conclusion based on 19 randomized controlled trials: High-dosage (>=400 IU/d) vitamin E supplements may increase all-cause mortality and should be avoided.

Health Hopes of Vitamin E • Heart Disease: Mixed results • Cancer: Promising but not conclusive – Breast cancer: two opposing studies – Colon and G. I. cancer: probably no benefit – Prostate and bladder cancer: possible benefit • Alzheimer’s: theoretical but not well studied

Vitamin E & Cataracts • 1998: “Antioxidant vitamins and nuclear opacities: the longitudinal study of cataract” – Cataract risk reduced by ½ in Vit E supplement users – 764 participant observational study (low significance) However, • 1997: “Long-term supplementation with alphatocopherol and beta-carotene and age-related cataract” – No benefit to Middle-aged male smokers taking vitamin E supplements on the incidence of cataract formation