Vitamin E is a group of compounds (including tocopherols and
tocotrienols) that have similar biologic activities. The most
biologically active is α-tocopherol, but β-, γ-, and
δ-tocopherols, 4 tocotrienols, and several stereoisomers may
also have important biologic activity. These compounds act as
antioxidants, which prevent lipid peroxidation of
polyunsaturated fatty acids in cellular membranes. Plasma
tocopherol levels vary with total plasma lipid levels. Normally,
the plasma α-tocopherol level is 5 to 20 μg/mL (11.6 to 46.4
µmol/L). High-dose vitamin E supplements do not protect against
cardiovascular disorders; whether supplements can protect
against Alzheimer disease and tardive dyskinesia or increase or
decrease the risk of prostate cancer is controversial. Although
the amount of vitamin E in many fortified foods and supplements
is given in IU, current recommendations are to use mg. Vitamin E
Deficiency Dietary vitamin E deficiency is common in developing
countries; deficiency among adults in developed