Should You Take Vitamin C and E Supplements?
For: Should You Still Take Vitamin E?, February
2003
Last year the Food and Nutrition Board
of the National Academy of Sciences—the main authority in the U.S.
for nutritional recommendations—published a major report on antioxidant
nutrients, including vitamins C and E. It
concluded that taking antioxidant 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