C and E Research
You Take Vitamin C and E Supplements?
year the Food and Nutrition Board of the National Academy of
Sciencesthe main authority in the U.S. for nutritional
recommendationspublished a major report on antioxidant
nutrients, including vitamins C and E. It
concluded that taking antioxidant supplements serves no purpose.
the Editorial Board of this newsletter, along with Gladys Block
(Professor of Public Health at UC Berkeley) and Bruce Ames (Professor
Emeritus of Biochemistry and Microbiology), reviewed the Food
and Nutrition Board report. Following this review, the recommendation
has been modified for vitamin E to 200 to 400 IU a day (instead
of up to 800 IU). It is widely recommended to ingest 250 to
500 milligrams of vitamin C, but suggest you get this from food,
is a review of the research behind the Food and Nutrition Board
report, and important conclusions.
different kinds of research
has shown that as antioxidants, these vitamins help inactivate
free radicals. The latter are unstable molecules (usually oxygen)
produced in the normal process of "burning" oxygen
for energy; they are also created by such environmental factors
as tobacco smoke and radiation. Free radicals can damage the
basic structure of cells and thus may lead to disease (notably
cancer and heart disease) and accelerate the aging process.
By mopping up free radicals, vitamins C and E could potentially
protect against these disorders.
laboratory and animal studies suggest
that vitamins C and E help reduce the risk of coronary artery
disease in a number of ways. First, they inhibit the oxidation
of LDL ("bad") cholesterol, both individually and
through their interaction. Oxidation makes LDL more likely to
promote the buildup of fatty plaque in coronary artery walls
(atherosclerosis). Vitamin E may also reduce the blood's ability
to clot, thus lowering the risk of heart attacks. Finally, E
may help reduce inflammatory processes (inflammation has been
linked with coronary artery disease).
large population studies have found
that people who consume the most vitamin C from foods have a
reduced risk of heart disease and various cancers. (Hence the
recommendation to eat at least five fruits and vegetables a
day.) Some population studies have found similar protective
effects from C or E supplements. But other elements in foods
rich in C, or something about the life-style of people who consume
high levels of C or E as supplements, may account for their
lower risk. These observational studies are unable to tease
apart the effects of various dietary constituents and simply
can't tell us whether taking large doses of E and/or C is beneficial.
the clinical trials show
well-designed clinical trials, using human subjects under carefully
controlled experimental conditions, have found that vitamins
C and E do have the proposed health benefits. But others have
found no effect. Different studies use different doses of vitamins,
so it's often hard to compare the results. Most have focused
on coronary artery disease.
E. The results have been inconclusive.
A study from Cambridge University, published in the Lancet
in 1996, for in-stance, found that among men with heart disease,
400 to 800 IU of E supplements a day for an average of 1.5 years
substantially reduced the risk of heart attack, but not death
rates. (Later, however, the researchers reanalyzed the data
and did find that vitamin E markedly reduced deaths from coronary
artery disease.) But the Heart Outcomes Prevention Evaluation
Study, a Canadian study published last year, found no benefit
when those at high risk for cardiovascular disease took 400
IU of E a day for four years. An Italian study published in
in 1999 found no significant reduction in coronary risk from
300 IU of E. These studies, and several others, raised more
questions than they answered. Most of the clinical trials have
been done on patients with heart disease. It's possible that
there would be a more consistently protective effect in healthy
research suggests that vitamin E supplements may lower the risk
of some types of cancer, as well as arthritis, Parkinson's,
one kind of stroke, diabetes, and Alzheimer's. But the evidence
is inconsistent and/or preliminary.
C. Several controlled studies have
found that large doses of vitamin C help relax blood vessels
and maintain blood flow (by increasing the amount of nitric
oxide produced in the arterial walls). Theoretically, this should
reduce the risk of cardiovascular disease. However, there have
been no large-scale studies to demonstrate that high doses of
vitamin C supplements actually prevent heart attacks.
grounds for concern
possible that antioxidant supplements in high doses, unlike
the nutrients in food, may upset the antioxidant balance in
the body. The many types of antioxidants do different kinds
of work, and they often work together. Notably, vitamins C and
E work well together to produce their antioxidant effect and
help protect each other from oxidation. They may also help other
antioxidants, such as beta carotene, do good work.
investigators have found that vitamin C can become a "pro-oxidant"
(have the opposite effect and actually become a free radical)
in the test tube. But there's no convincing evidence that this
happens in the body. (Similarly, many other substances, often
marketed as supplements, have antioxidant effects in the test
tube, but probably not in the body.)
many people get 250 to 500 milligrams (or more) of vitamin C
from a diet rich in fruits and vegetables, with no adverse effects,
it's relatively safe to get that much from supplements. In the
case of vitamin E, however, since few, if any, people get the
recommended 200 to 400 IU from food, we must be concerned with
safety. Nonetheless, long-term studies have found virtually
no adverse effects from these levels of E. In fact, the report
of the Food and Nutrition Board concluded that 1,000 IU per
day is the safe upper limit for vitamin E supplements (the upper
limit for C, it said, is 2,000 milligrams).
are only beginning to understand the importance of antioxidants
and how they work. The evidence is still accumulating and may
look different to different experts. Some important studies
on C and E are underway and should answer many of the questions
in the next few years.
Consume 250 to 500 milligrams
of vitamin C per day. Such levels
are considered safe and the potential benefits are great. If
you eat five or more servings of fruits and vegetables and their
juices, as recommended, you can easily get that much vitamin
C. If not, take a supplement.
200 to 400 IU of vitamin E supplements per day.
You can't get that much from food unless you eat huge amounts
of nuts, seeds, or vegetable oil, all high in fat. Not all experts
agree that E supplements are advisable. But the majority believe
that such levels are safe and potentially beneficial. Vitamin
E is a complex group of related compounds. Look for "natural"
vitamin E supplements (preferably those containing some "mixed
tocopherols"), since synthetic E largely contains forms
that are poorly utilized by the body.
Reference Source 98,99,101