Should You Take Vitamin C and E Supplements?
For: Cholesterol Drugs and Vitamins Add Up to a Surprise, March
2002
Last year the Food and Nutrition
Board of the National Academy of Sciences—the main authority
in the U.S. for nutritional re-commendations—published a major
report on antioxidant nutrients, including vitamins C and E. It
concluded that taking anti-oxidant supplements serves no purpose.
The WELLNESS LETTER has for years
advised readers to take vitamin C and E pills. We based this recommendation
on the belief that these supplements are safe and that they may
reduce the risk of heart disease, cancer, cataracts, and other disorders.
However, some recent research on these vitamins, including several
well-publicized studies, has had disappointing or confusing results.
The experts thus remain divided about C and E supplements.
Recently 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, we have modified our advice somewhat. We
have lowered our recommendation for vitamin E to 200 to 400 IU a
day (instead of up to 800 IU). We continue to recommend 250 to 500
milligrams of vitamin C, but suggest you get this from food, if
possible.
Here is our review of the research
behind the Food and Nutrition Board report, plus our conclusions.
The different kinds of research
Much laboratory
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.
Many
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).
Many 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.
What the clinical trials show
Some 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.
Vitamin 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 the Lancet
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 people.
Other 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.
Vitamin 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.
Some grounds for concern
It's 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.
Some 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, as
we reported in May 2000. (Similarly, many other substances, often
marketed as supplements, have antioxidant effects in the test tube,
but probably not in the body.)
Since many people get 250 to
500 milligrams (or more) of vitamin C from a diet rich in fruits
and vegetables, with no adverse effects, we feel it's 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).
Scientists 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.
Our bottom line
•
Consume 250 to 500 milligrams of vitamin
C per day. We are convinced that such
levels are safe and that 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.
• Take 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 members of our Editorial Board 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. For more about natural vitamin E, see "Vitamin E: Is Natural Better," WELLNESS LETTER, September 1999.
UC Berkeley Wellness Letter, June 2001
