About Vitamin E ビタミンEtoh
VITAMIN E
Vitamin E is the collective name for a group of fat-soluble compounds with distinctive anti-oxidant
activities. (16) Naturally occurring vitamin E exists in eight distinct chemical forms: alpha-, beta-, gamma-,
and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol. The different forms of vitamin
have varying levels of biological activity. (16) Alpha- (or α-) tocopherol is the form that has been studied
most extensively. Almost all published studies of Vitamin E have looked at the effects of α-tocopherol.
Vitamin E is a fat-soluble anti-oxidant that stops the production of reactive oxygen species (ROS) or free
radicals formed when fat undergoes oxidation. (17) Scientists are investigating whether, by limiting freeradical production and possibly through other mechanisms, vitamin E might help prevent or delay the
chronic diseases associated with free radicals.
In addition to its activities as an anti-oxidant, vitamin E is involved in immune function as well as cell
signaling, regulation of gene expression, and other metabolic processes. (16) Alpha-tocopherol inhibits
the activity of protein kinase C, an enzyme involved in cell proliferation and differentiation in smooth
muscle cells, platelets, and monocytes. (18) Endothelial cells with adequate levels of Vitamin E, lining the
interior surface of blood vessels, are better able to resist blood-cell components adhering to this surface.
Vitamin E also increases the expression of two enzymes that suppress arachidonic acid metabolism,
thereby increasing the release of prostacyclin from the endothelium, which, in turn, dilates blood vessels
and inhibits platelet aggregation. (18)
Three national surveys—the 2001–2002 NHANES (19), NHANES III (1988–1994) (19), and the
Continuing Survey of Food Intakes by Individuals (1994–1996) (20)—have found that the diets of most
Americans provide less than the RDA levels of vitamin E.
Heart Health
There are several lines of evidence that vitamin E could help prevent or delay coronary heart disease. In
vitro studies have found that α-tocopherol inhibits oxidation of low-density lipoprotein (LDL) cholesterol,
which is thought to be a crucial initiating step for atherosclerosis. (18) Vitamin E might also help prevent
the formation of blood clots that could lead to a heart attack or venous thromboembolism. (21)
Several epidemiological studies have associated lower rates of heart disease with higher vitamin E
intakes. One study of approximately 90,000 nurses found that the incidence of heart disease was 30% to
40% lower in those with the highest intakes of vitamin E. (22) In another study of 5,133 Finnish men and
women followed for a mean of 14 years, higher vitamin E intakes from food were associated with
decreased mortality from Chronic Heart Disease (CHD). (23)
However, the latest published clinical trial of vitamin E's effects on the heart and blood vessels of women
included almost 40,000 healthy women ≥45 years of age. These women were randomly assigned to
receive either 600 IU of natural vitamin E on alternate days or placebo and who were followed for an
average of 10 years. (24) The investigators found no significant differences in rates of overall
cardiovascular events (combined nonfatal heart attacks, strokes, and cardiovascular deaths) or all-cause
mortality between the groups. However, the study did find two positive and significant results for women
taking vitamin E: they had a 24% reduction in cardiovascular death rates, and those ≥65 years of age had
a 26% decrease in nonfatal heart attack and a 49% decrease in cardiovascular death rates.
Eye Health
Vitamin E supplements, taken alone or in combination with other anti-oxidants, may reduce the risk of
developing macular degeneration or cataracts. The Age-Related Eye Disease Study (AREDS), a large
randomized clinical trial, revealed that participants with early-stage age-related macular degeneration
(AMD) could slow the progression of their disease by taking a daily supplement of vitamin E (400 IU dlalphatocopheryl acetate), vitamin C (500 mg), beta-carotene (15 mg), zinc (80 mg), and copper (2 mg) for
an average of 6.3 years compared to participants taking a placebo. (25)