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Nutrition, Vitamins & Supplements for Seniors
Vitamin E Studies Have Been Fatally Flawed for Years
Says New Study
Amount needed to reduce oxidative stress far higher
than used in clinical trials
Sept. 24, 2007 – Many senior citizens have kept a
close eye on research about Vitamin E after studies indicated it could
provide protection from heart disease, the number one killer of the
elderly. But, the research to determine the power of Vitamin E to reduce
oxidative stress and, therefore, preventing cardiovascular disease, has
produced widely varying results. Now researchers say generations of
studies on vitamin E may be largely meaningless, because the levels
necessary to reduce oxidative stress are far higher than those that have
been commonly used in clinical trials.
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In a new study and commentary in Free Radical
Biology and Medicine, researchers concluded that the levels of vitamin E
necessary to reduce oxidative stress – as measured by accepted
biomarkers of lipid peroxidation – are about 1,600 to 3,200 I.U. daily,
or four to eight times higher than those used in almost all past
clinical trials.
This could help explain the inconsistent results of
many vitamin E trials for its value in preventing or treating
cardiovascular disease, said Balz Frei, professor and director of the
Linus Pauling Institute at Oregon State University, and co-author of the
new commentary along with Jeffrey Blumberg, at the Jean Mayer USDA Human
Nutrition Research Center on Aging at Tufts University.
“The methodology used in almost all past clinical
trials of vitamin E has been fatally flawed,” said Frei, one of the
world’s leading experts on antioxidants and disease.
“These trials supposedly addressed the hypothesis
that reducing oxidative stress could reduce cardiovascular disease. But
oxidative stress was never measured in these trials, and therefore we
don’t know whether it was actually reduced or not. The hypothesis was
never really tested.”
Amount needed to be effective is above
recommendations
The level of vitamin E that clearly can be shown to
reduce oxidative stress, new research is showing, is far higher than the
level that could be obtained in any diet, and is also above the
“tolerable upper intake level” outlined by the Institute of Medicine,
which is 1,000 I.U. a day.
OSU researchers are not yet recommending that
people should routinely take such high levels, but they do say that
controlled clinical trials studying this issue should be aware of the
latest findings and seriously consider using much higher vitamin E
supplement levels in their studies.
In lab, animal or human studies, there’s evidence
that vitamin E can reduce oxidative stress, inhibit formation of
atherosclerotic lesions, slow aortic thickening, lower inflammation, and
reduce platelet adhesion.
Some human studies using lower levels of vitamin E
supplements, such as 100 to 400 I.U. a day, have shown benefits in
reducing cardiovascular disease risk, and others have not. An underlying
assumption was that these levels were more than adequate to reduce
oxidative stress, since they far exceeded the “recommended dietary
allowance” or RDA for the vitamin, a level adequate to prevent
deficiency disease.
“What’s now clear is that the amount of vitamin E
than can conclusively be shown to reduce oxidative stress is higher than
we realized,” Frei said.
“And almost none of the studies done with vitamin E
actually measured the beginning level or reduction of oxidative stress.”
Proper studies of vitamin E, researchers say, must
be done carefully and take into account the newest findings about this
micronutrient. It’s now known that natural forms of the vitamin are far
more readily absorbed than synthetic types. It’s also been discovered
that supplements taken without a fat-containing meal are largely
useless, because in the absence of dietary fat vitamin E is not
absorbed.
Some clinical trials may wish to study the long
term effect of vitamins on healthy individuals. But if a clinical trial
seeks to learn the value of reducing oxidative stress, they should
select patients in advance for those who have high, measurable oxidative
stress – often people who are older or have a range of heart disease
risk factors, such as obesity, poor diet, hypertension or other
problems.
Cognizance should also be taken of people with
health issues that may further increase their vitamin needs, such as
smokers.
“A pill count simply isn’t enough to determine the
value of vitamin E,” Frei said. “We need to select people for trials
properly, make sure they are taking the right form of the vitamin, at
the right levels and at the right time, and then verify the metabolic
results with laboratory testing.”
“Only when we do these studies right will we answer
questions about the value of vitamin E in addressing cardiovascular
disease,” he said. “So far we’ve been flying blind.”
A parallel, Frei said, would be presuming to test
the value of a statin drug, which lowers cholesterol, without ever
measuring cholesterol levels in the test subjects, neither at the
beginning nor at the end of the study. Such trials would be ridiculed in
the science community.
So far, that’s the way vitamin E has been studied.
The use and intake of vitamins, experts say, has
traditionally been thought of in terms of overt deficiency – for
example, not enough vitamin C causes scurvy. Much less research has been
done on the levels that can help create optimum health. The issue is of
special importance with modern populations that have very different
diets, activity levels and increased lifespan, and are dying from much
different causes – predominantly heart disease and cancer – than people
of past generations.
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