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Without vitamin E, we
essentially turn rancid. Vitamin E is fat-soluble, that is, able to
penetrate the fatty areas of our tissues. As it does so, it
neutralizes toxic oxidants and protects oxidant-sensitive
membranes. Thus vitamin E is justifiably known as an antioxidant,
and for helping to prevent age-associated increases in oxidative
insults to our bodies.
The Eight Forms of Vitamin E
In
reality, vitamin E comes in eight different forms, all of which are
derived from plants. The eight E's are divided into two
classes:
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The tocopherols consist of
4 types of vitamin E, alpha, beta, gamma, and delta. The features
distinguishing each are slight chemical differences (location and
number of methyl groups) on its core structure.
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The tocotrienols are
virtually identical to the tocopherols in structure, except for the
presence of 3 unsaturated bonds (hence trienol). Alpha, beta, gamma
and delta tocotrienols are more permeable to cell membranes because
of their unsaturated bonds. This chemical difference imparts
certain advantages over the less permeable tocopherols.
The
most potent antioxidant of the group is alpha tocopherol. For
reasons still unknown, this form of E represents the bulk of
vitamin E present in our serum. This is puzzling, since the plants
we normally consume contain much more gamma tocopherol. Scientists
originally speculated that our bodies require high serum levels of
alpha tocopherol and have developed mechanisms to retain it. Thus,
multi-vitamins almost always contain alpha tocopherol.
It
is becoming more evident, however, that all forms of E are
important and that they serve very different functions. Laboratory
experiments have indicated that gamma and alpha tocopherol may
complement one another with respect to antioxidant protection.
Alpha tocopherol is most effective at neutralizing oxygen-based
free radicals, whereas gamma tocopherol does best with
nitrogen-based free radicals. Both types of radicals are
destructive to our bodies.
The
vitamin E offered on the market is either man-made or isolated from
plants. Man-made (or synthetic) vitamin E is designated on the
bottle's label as DL alpha tocopherol. The D and L are isomers or
mirror images of each other. Only the D form is representative of
the natural vitamin E alpha tocopherol. There is considerable
controversy as to whether the L form interferes with the natural D
form in the body. Some researchers believe it may be
toxic.
Natural vitamin E is
usually labeled D alpha tocopherol but almost always contains all 4
tocopherols. Typically, the bottle's label mentions only D alpha
tocopherol because of the expense the manufacturer would incur to
assay for the presence and quantity of the other three. The 4
tocopherols are derived from soybean oil or, less commonly, wheat
germ. The 4 tocotrienols are usually prepared from extracts of palm
oil or rice bran.
Vitamin E deficiency is not
common, but it can occur with poor nutrition and/or a problem with
absorption of fats. The RDA for vitamin E is 30 International Units
(IU) per day for DL and 22 IU/day for D alpha tocopherol. A diet
totally devoid of fats can result in a deficiency of E, since some
fat is required for absorption from the intestines.
Fragile red blood cells are
a common characteristic of E deficiency. Blood cell membranes,
normally protected by E, tend to oxidize and rupture easily. Recent
studies indicate vitamin E may help in slowing cognitive decline in
Alzheimer's patients, and it may even lower blood pressure and
cholesterol levels. Significant evidence also supports the vitamin
as important for protecting tissues from the destructive action of
oxidants and consequent disease, including heart disease,
cataracts, cancer, neurological disorders and disorders of the
muscular system. The incidence of these diseases increases with
age. Thus it is important to obtain enough E to attenuate the
age-associated destructive process.
Vitamin E is more than an
antioxidant. Growing evidence supports specific roles for the
different forms of vitamin E. For example, recent research
demonstrates gamma tocopherol to be capable of blocking the
activity of an enzyme involved in producing cellular mediators of
inflammation (prostaglandins), which can lead to disease. Other
tocopherols, including the more popular alpha, are largely
ineffective in this context.
Alpha tocotrienol has now
been shown in cell culture experiments to protect cells of the
nervous system from the degenerative action created by the
overproduction of the neurotransmitter, glutamate. This chemical,
better known as monosodium glutamate, is used as a food enhancer
and is infamous for its reputation as the agent responsible for the
Chinese restaurant syndrome (bad headaches, etc.) in those who
consume too much of it. Normally, an excess of this
neurotransmitter activates a neurotoxic enzyme (12-LOX).
Tocotrienol, in very small amounts, stops this toxic enzyme in its
tracks, thus potentially protecting the nervous tissue.
The
unique behavior of the different forms of vitamin E helps explain
the advice of nutritionists to consume a variety of fruits,
vegetables, legumes and grains. All are good sources of the various
forms of vitamin E. Grains should preferably be non-refined. The
tocotrienols, as well as other micronutrients, are present in the
rice bran, which is lost in processing. People on low-fat diets,
such as vegans, are often deficient in vitamin E and should
consider taking supplements.
How
much E should one take, if any? The upper safe limit for D alpha
tocopherol is 1,500 IU/day, according to The Institute of Medicine.
The major danger in taking high levels of E is its capacity to
inhibit the adherence of platelets to the walls of blood vessels.
This is positive for cardiovascular health in those with
over-active clotting, but too much E can cause bleeding, especially
for people taking other anticoagulants, such as aspirin or
coumadin. If you are inclined to take vitamin E, 400 IU/day of
natural vitamin E is a reasonable target. However, it is advisable
to consult with your physician before taking this
supplement.
Finally, the E vitamins
function as antioxidants only in their reduced, non-oxidized state.
In a subsequent newsletter we will describe how the cells of the
body maintain these antioxidants in their reduced or active state.
We will also describe how the versatile antioxidant, alpha lipoic acid,
functions to recycle these and other antioxidants to maintain
cellular health as we age.
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Substantial progress has
been made in understanding the bio- chemistry of the mitochondria -
the organelles that power our cells. Similarly, mitochondrial decay
is broadly recognized as playing a central role in the aging
process. However, much less is known about effective nutritional
approaches to maintain and promote mitochondrial health.
A recent literature review
in Canada has evaluated the effects of a wide variety of substances
that are reported to produce positive effects on the mitochondria.
These include coenzyme Q10; other antioxidants, such as
ascorbic acid, vitamin E, and lipoic acid; niacin; creatine;
carnitine, and some others. For further information, click here.
This Research Update
column highlights articles related to recent scientific inquiry
into the process of human aging. It is not intended to promote any
specific ingredient, regimen, or use and should not be construed as
evidence of the safety, effectiveness, or intended uses of the
Juvenon product. The Juvenon label should be consulted for intended
uses and appropriate directions for use of the
product.
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