Tocopherol, or Vitamin E, is a fat-soluble vitamin in eight forms that is an
important antioxidant. Vitamin E is often used in skin creams and lotions because it
is believed to play a role in encouraging skin healing and reducing scarring after
injuries such as burns.
Natural vitamin E exists in eight different forms or isomers, four tocopherols and
four tocotrienols. Each form has its own biological activity, the measure of potency
or functional use in the body. Alpha-tocopherol is traditionally recognized as the
most active form of vitamin E in humans, and is a powerful biological antioxidant.
The measurement of "vitamin E" activity in international units (IU) was based on
fertility enhancement by the prevention of spontaneous abortions in pregnant rats
relative to alpha tocopherol. The other isomers are slowly being recognized as
research begins to elucidate their additional roles in the human body. Many
naturopathic and orthomolecular medicine advocates suggest that vitamin E supplements
contain at least 20% by weight of the other natural vitamin E isomers. Commercially
available blends of natural vitamin E include "mixed tocopherols" and "high gamma
tocopherol" formulas.
Antioxidants such as vitamin E act to protect cells against the effects of free
radicals, which are potentially damaging by-products of the body's metabolism. Free
radicals can cause cell damage that may contribute to the development of
cardiovascular disease and cancer. Studies are underway to determine whether vitamin
E might help prevent or delay the development of those chronic diseases.
Vegetable oils, nuts, wheat germ and green leafy vegetables are the main dietary
sources of vitamin E. Fortified breakfast cereals are also an important source of
vitamin E in the United States.
The Recommended Daily Allowance for vitamin E is based on the alpha-tocopherol form
because it is the most active, or usable, form as usually tested. Unlike other
vitamins, the synthetic form of alpha-tocopherol, produced from isophytol and found
in many supplements, is not identical to the natural form, containing seven extra
alpha tocopherol epimers as well as the natural isomer. The synthetic form
(all-racemic alpha tocopherol also frequently marked as "d,l-alpha tocopherol") is
not as active as the natural alpha tocopherol form. Information on any side effects
of the synthetic epimers is not readily available.
Results of two national surveys, the National Health and Nutrition Examination Survey
(NHANES III 1988-91) and the Continuing Survey of Food Intakes of Individuals (1994
CSFII) indicated that the dietary intake of most Americans does not provide the
recommended intake for vitamin E. However, a 2000 Institute of Medicine (IOM) report
on vitamin E states that intake estimates of vitamin E may be low because energy and
fat intake is often underreported in national surveys and because the kind and amount
of fat added during cooking is often not known. The IOM states that most North
American adults get enough vitamin E from their normal diets to meet current
recommendations. However, they do caution individuals who consume low fat diets
because vegetable oils are such a good dietary source of vitamin E. "Low-fat diets
can substantially decrease vitamin E intakes if food choices are not carefully made
to enhance alpha-tocopherol intakes".
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