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Vitamin E and heart disease:
Preliminary research has led to a belief that vitamin E
may help prevent or delay coronary heart disease.
Researchers have reported that oxidative changes to
LDL-cholesterol (sometimes called "bad" cholesterol) promote
blockages "atherosclerosis" in coronary arteries that may
lead to heart attacks.
► Vitamin E may help prevent or
delay coronary heart disease by limiting the oxidation of
LDL-cholesterol.
► Vitamin E also may help
prevent the formation of blood clots, which could lead to a
heart attack.
Support for the role of vitamin E in heart disease
prevention has come from observational studies, particularly
2 cohort studies which were published in 1993:
In the 1st study:
The Nurses' Health Study, the researchers concluded that
among 83,234 middle-aged women who participated in the
study, there was a 40% reduced risk of coronary artery
disease for those who took vitamin E supplements compared to
those who did not (New England Journal of Medicine 1993;
328: 1444-9).
The 2nd study:
The Health Professionals Follow-up Study, involved over
39,000 males and showed evidence of a significant
association between a high intake of vitamin E from
supplements and a lower risk of heart disease (New England
Journal of Medicine 1993; 328:1450-1456).
A 1994 review of 5,133 Finnish men and women aged 30-69
years also suggested that increased dietary intake of
vitamin E was associated with decreased mortality (death)
from heart disease.
The results of at least 5 large observational studies
suggest that increased vitamin E consumption is associated
with a decreased risk of myocardial infarction (heart
attack) in both women and men. Each study was a prospective
study that measured vitamin E consumption in presumably
healthy people and followed them for several years to
determine how many of them were diagnosed with, or died as a
result of heart disease.
Even though these observations are promising, randomized
clinical trials raise questions about the efficacy of
vitamin E supplements in the prevention of heart disease.
The Heart Outcomes Prevention Evaluation (HOPE) Study
followed almost 10,000 patients for 4.5 years who were at
high risk for heart attack or stroke:
In this intervention study the subjects who received 265 mg
(400 IU) of vitamin E daily did not experience significantly
fewer cardiovascular events or hospitalizations for heart
failure or chest pain when compared to those who received a
placebo (sugar pill). The researchers suggested that it is
unlikely that the vitamin E supplement provided any
protection against cardiovascular disease in the HOPE study.
This study is continuing, with the goal of determining
whether a longer duration of intervention with vitamin E
supplements will provide any protection against
cardiovascular disease.
In a study sponsored by the National Heart, Lung, and
Blood Institute (NHLBI) of the National Institutes of
Health:
Postmenopausal women with heart disease who took supplements
providing 400 IU vitamin E and 500 mg vitamin C twice a day,
either alone or in combination with hormones, did not have
fewer heart attacks or deaths. There was also no change in
progression of their coronary disease.
The Women's Angiographic Vitamin and Estrogen (WAVE)
trial:
Studied 423
Postmenopausal women at seven clinical centers
in the U.S. and Canada. In postmenopausal women with
coronary disease enrolled in this trial, neither hormone
replacement therapy nor antioxidant vitamin supplements
provided cardiovascular benefit.
While 100 IU or more of supplemental vitamin E per day has
been shown to reduce the risk of heart attacks in healthy
individuals, those with pre-existing coronary artery disease
often take 800 to 1200 IU/day based on the pioneering work
of the Shute brothers in the mid 1940s.
Results of the Women's Health Study, the Women's Antioxidant
and Cardiovascular Study and the SUVIMAX study, all of which
are investigating the effects of vitamin supplements on the
progression of coronary heart disease, are due in 2005 and
will provide additional information on the association
between vitamin E supplements and cardiovascular disease.
Vitamin E and cancer:
The evidence is not as clear-cut when it comes to cancer
and vitamin E. Many types of cancer are believed to result
from oxidative damage to DNA caused by free radicals.
- Antioxidants - such as
vitamin E - help protect against the damaging effects of
free radicals, which may contribute to the development of
chronic diseases such as cancer.
- Vitamin E also may block
the formation of nitrosamines, which are carcinogens
formed in the stomach from nitrites consumed in the diet.
- Vitamin E may also protect
against the development of cancers by enhancing immune
function.
However, human trials and surveys which tried to associate
vitamin E with incidence of cancer have generally been
inconclusive.
The Nurses Health Study:
Which we referred to earlier, studied 83,234 women at
baseline and sought to assess the incidence of breast cancer
during a 14-year follow-up. The study showed that
pre-menopausal women with a family history of breast cancer
who consumed the highest quantity of vitamin E enjoyed a 43%
reduction in breast cancer incidence compared to only a 16%
risk reduction for women without a family history of breast
cancer.
Based on this study, vitamin E appears to protect against
genetic-predisposed breast cancer better than
environmentally-induced breast cancer.
However other studies which have reviewed the effects of
standard vitamin E products (alpha-tocopherol acetate) taken
by themselves have failed to decisively show a protective
benefit for cancer.
It is possible that other forms of vitamin E found in food
(such as gamma tocopherol and tocotrienols) may be
responsible for providing the protective effect against
breast cancer shown in some surveys which evaluated total
vitamin E intake. So it is recommended that, when selecting
a vitamin E supplement, choosing the one which contains
other tocopherols and tocotrienols, not just
alpha-tocopherol.
Certain vitamin E compounds found in food confer a
significant protective effect, but that commercial
alpha-tocopherol acetate supplements fail to reduce the
incidence of breast cancer for most women. The data
indicates that some other vitamin E compounds in food may
account for the dramatic reductions in breast cancer
incidence when dietary intake levels of vitamin E are
measured.
Most studies have indicated that the form of vitamin E used
in most commercial preparations (alpha-tocopherol acetate)
has not been shown to protect against breast cancer.
The tocotrienols:
- It is a one of the 8 members
of the vitamin E family, which have demonstrated the most
significant potential to not only reduce breast cancer
incidence, but also to inhibit the propagation of existing
breast cancer cells.
- The objective of any cancer
therapy is to induce the cancer cells to differentiate in a
way which promotes programmed cell death (apoptosis).
Several studies indicate that tocotrienols induce breast
cancer cell apoptosis.
- Tocotrienolshave been shown to
inhibit the growth of estrogen receptor positive breast
cancer cells by as much as 50% in culture.
It therefore appears that the individual tocopherol and
tocotrienols have different biological activities as they
relate to their effects on health, and it is recommended
that, when choosing a vitamin E product, the selection one
which also contains other tocopherol and tocotrienols, not
just alpha-tocopherol.
It is especially important to take the tocotrienols along
with some form of oil or fat-containing food. When
tocotrienols are taken on an empty stomach, absorption is
reduced by an average of 50%,so when taking tocopherol
and/or tocotrienol vitamin E supplements, it is better to
take them with a meal or with fatty acid capsules like fish
oil (EPA-DHA) e.g. " Omega 3 plus".
Prostate cancer: Some evidence associates higher intake of
vitamin E with a decreased incidence of prostate cancer
although the evidence is not overwhelming.
The American Cancer society recently released the results of
a long-term study that evaluated the effect of regular use
of vitamin C and vitamin E supplements on bladder cancer
mortality in almost 1,000,000 adults in the U.S. The study,
conducted between the years 1982 to 1998, found that
subjects who regularly consumed a vitamin E supplement for
longer than 10 years had a reduced risk of death from
bladder cancer. No benefit was seen from
vitamin C
supplements.
Vitamin E and cataracts:
Cataracts are abnormal growths in the lens
of the eye. These growths cloud vision. Cataracts also
increase the risk of disability and blindness in aging
adults.
Antioxidants are being studied to determine whether they can
help prevent or delay cataract growth.
Observational studies have found that lens clarity, which is
used to diagnose cataracts, was better in regular users of
vitamin E supplements and in persons with higher blood
levels of vitamin E.
A study of middle-aged male smokers, however, did not
demonstrate any effect from vitamin E supplements on the
incidence of cataract formation.
The effects of smoking, a major risk factor for developing
cataracts, may have overridden any potential benefit from
the vitamin E, but the conflicting results also indicate a
need for further studies before researchers can confidently
recommend extra vitamin E for the prevention of cataracts.
Vitamin E and lipid peroxidation:
Lipid peroxidation refers to the oxidative degradation
of lipids. It is the process whereby free radicals "steal"
electrons from the lipids in cell membranes, resulting in
cell damage. This process proceeds by a free radical chain
reaction mechanism. It most often affects polyunsaturated
fatty acids, because they contain multiple double bonds in
between which lie methylene -CH2- groups that are especially
reactive hydrogen. As with any radical reaction the reaction
consists of three major steps: initiation, propagation and
termination.
Currently, the biological activity of Vitamin E is to
prevent lipid peroxidation. Since alpha-tocopherol is the
most active tocopherol against peroxyl radicals (LOO.) and
delta-tocopherol is the least active
(alpha>beta=gamma>delta). The anti-oxidant activity of
Vitamin E is based on the ease with which the hydrogen on
the hydroxyl group of the chroman ring can be donated to
neutralize a free radical (creating a more stabile
tocopheroxyl radical).
Vitamin E and the immune system:
Vitamin E is particularly protective against
exercise-induced free radicals. For a healthy non-smoking
person seeking to boost immune system function, reduce
cancer risk and reduce membrane lipid peroxidation damage
during exercise (or protect mitochondria in general) through
Vitamin E supplementation, a mixture of alpha-tocopherol and
gamma-tocopherol supplements would be prudent- along with
supplementation with Co-Enzyme Q10 and
Vitamin K.
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