Vitamins: More May Be Too Many
April 29, 2003
By GINA KOLATA
A growing number of medical experts are concerned that
Americans are overdoing their vitamin consumption. As many
as 70 percent of the population is taking supplements,
mostly vitamins, convinced that the pills will make them
healthier.
But researchers say that vitamin supplements cannot correct
for a poor diet, that multivitamins have not been shown to
prevent any disease and that it is easy to reach high
enough doses of certain vitamins and minerals to actually
increase the risk of disease.
No longer, the experts say, are they concerned about
vitamin deficits. Those are almost unheard of today, even
with the population eating less than ideal diets and
skimping on fruits and vegetables. Instead, the concern is
with the dangers of vitamin excess.
"There has been a transition from focusing on minimum needs
to the reality that today our problem is excess - excess
calories and, yes, excesses of vitamins and minerals as
well," said Dr. Benjamin Caballero, a member of the Food
and Nutrition Board at the National Academy of Sciences and
the director of the Center for Human Nutrition at Johns
Hopkins University.
Dr. Caballero said that for some supplements, including
vitamin A, the difference between the recommended dose and
a dose that could lead to bad outcomes like osteoporosis
was not large. Popular multivitamins, he added, often
contain what could be risky doses.
"Certainly," he said, "by consuming supplements, people can
reach that level."
Doctors who once told patients that multivitamins were, at
worst, a waste of money now say they are questioning that
idea.
"All of a sudden, scientists are rearing back and saying,
`Wait a minute, do we really know that we need this and do
we really know that we need that?' " said Dr. Ruth Kava,
nutrition director at the American Council on Science and
Health, a consumer foundation in Manhattan that is in part
financed by industry.
With vitamin A in particular, it is easy to step over the
edge into a danger zone, said Dr. Joan McGowan, chief of
the musculoskeletal diseases branch at the National
Institute of Arthritis and Musculoskeletal and Skin
Diseases.
"You can be eating Total cereal, drinking fortified milk,
taking a multivitamin," Dr. McGowan said. "You can get into
a situation where you're getting more than you need. Until
recently, there was little concern about vitamin A and bone
health."
Now, she added, "we may have to rethink the issues."
Similar questions are being raised about other vitamins and
minerals, notably iron and vitamins E and C.
Researchers say the questions involve multivitamins taken
by healthy people, not specific vitamins or minerals taken
by groups with specific needs. Some elderly people, for
example, may be deficient in vitamin B12 because they lose
their ability to absorb it from foods. People who spend
little time outdoors may require vitamin D, which the skin
makes when it is exposed to sunlight. Even when older
people are in the sun, aging skin loses much of its ability
to synthesize the vitamin.
Pregnant women who do not receive enough folic acid, a
vitamin in fruits and vegetables that is added to enriched
flour, are at increased risk of having babies with neural
tube defects. Because the vitamin is needed at the very
start of pregnancy, some advocate folic acid supplements
for all who might become pregnant, just to be sure they are
protected.
For most people, however, the issue is not deficits.
Instead, nutrition researchers ask: Do people eating
relatively healthy diets with fresh fruits and vegetables
and not too many calories or fats benefit from
multivitamins or other supplements? Do those whose diets
are abysmal, heavy on fast foods and lacking in fruits and
vegetables, make up for some deficits if they take
multivitamin pills?
Dr. Annette Dickinson, president of the Council for
Responsible Nutrition, a group that represents the
supplement industry, says 70 percent of Americans sometimes
take supplements - usually multivitamins or individual
vitamins and minerals - and 40 percent take them regularly.
"Our position," she said, "is that most people, literally
most people, would benefit from taking a multivitamin every
day. It's insuring adequate and even generous intake of all
the nutrients."
The most popular individual supplements are vitamins C and
E, said Dr. Robert M. Russell, the director the Human
Nutrition Research Center of Agriculture Department at
Tufts University, who is head of the Food and Nutrition
Board. Scientists once thought those vitamins could help
prevent ailments like cancer and heart disease, but
rigorous studies found no such effects.
Vitamin E supplements can increase the risk of heart
attacks and strokes, and studies of vitamin C supplements
consistently failed to show that it had any beneficial
effects.
"The two vitamins that are the most not needed are the ones
most often taken," Dr. Russell said.
Excess vitamin C is excreted in the urine, but excesses of
some other vitamins are stored in fat, where they can build
up. Of particular concern, researchers say, is vitamin A.
It is found in liver, and small amounts are added to milk.
But for most people who are reaching worrisome levels, the
main source is supplements, multivitamins, nutrition bars,
health drinks and cereals.
Several recent large studies indicate that people with high
levels of vitamin A in their blood have a greater risk for
osteoporosis. People can easily reach a potentially
dangerous level, about five times the recommended dose, by
taking vitamins and supplements, nutrition researchers say.
Some popular multivitamins run 1,500 micrograms a pill,
twice the recommended daily amount and a level that, in one
recent study, doubled the risk of bone fractures. Some
supplements provide as much as 4,500 micrograms a day, well
above the level that the National Academy of Sciences calls
an upper limit for safety.
"If you have a good source of vitamin A in your food and
you take a supplement with another 100 percent, you can
easily reach a level that can accumulate" to one associated
with increased risk of osteoporosis, Dr. Caballero said.
Dr. Dickinson said that multivitamin manufacturers were
decreasing the vitamin A in their products, but that it
might take a year for the reformulated products to appear.
Others warn about overdosing on other vitamins and
minerals.
Dr. Richard J. Wood, director of the mineral
bioavailability laboratory at Tufts, worries about iron
overload, which can increase the risk of heart disease. In
a large federal research effort, the Framingham study, Dr.
Wood found that 12 percent of the elderly participants had
worrisome levels. "Hardly anyone had iron deficiency
anemia," he said. "But 16 percent were taking
iron-containing supplements."
While readily noting that the proof of a benefit is not in,
some researchers said they took multivitamins. They agree
with Dr. Joann E. Manson, chief of preventive medicine at
Brigham and Women's Hospital in Boston, who takes a
multivitamin and recommends it to patients whose diets seem
imbalanced.
"I think it's a good form of insurance," Dr. Manson said.
"I don't think there's a significant downside. We don't
have the evidence yet that it is beneficial."
Dr. Robert H. Fletcher, a professor of ambulatory medicine
at Harvard Medical School, also takes multivitamins. For
him, the deciding factor was whether he ingested enough
folic acid. Studies have suggested that high levels of
folic acid can protect against heart disease by lowering
levels of another substance, homocysteine. High levels of
homocysteine are associated with increased risks of heart
disease, but there is no study showing definitively that
reducing homocysteine levels protects against heart
disease.
So far, the folic acid studies are suggestive, not
definitive. But Dr. Fletcher said, "If I were a betting
man, I'd bet on it."
But a European study, reported recently at a meeting of the
American College of Cardiology, found that folic acid
supplements actually made matters worse for heart disease
patients. The study, the Folate After Coronary Intervention
Trial, involved 626 patients who were having stents
inserted into blocked arteries to keep them open. Half were
randomly assigned to take folic acid, and the rest took a
placebo. Six months later, the arteries of those taking
folic acid were significantly narrower than the arteries of
those taking a placebo, exactly the opposite of what the
investigators had expected.
A previous study, however, had found that folate helped
such patients. Dr. Eric Topol, an interventional
cardiologist at the Cleveland Clinic, said he thought the
truth was that it was neither helpful nor harmful for most
people. "Over all, the likely explanation is that there is
a neutral effect, and these relatively small trials found
opposite findings due to the play of chance," he said.
Dr. Topol said B vitamins, like folic acid, "can't be
recommended" at this point, except for people with
extremely high levels of homocysteine, and even then their
value has not been rigorously demonstrated.
Karen Miller-Kovach, chief scientist for Weight Watchers
International, has a compromise. She takes a child's
multivitamin, with its much lower levels of vitamins and
minerals.
"It is virtually impossible to find an adult multivitamin
and mineral supplement that is only 100 percent of the
R.D.A.," Ms. Miller-Kovach said. "All are 150 percent or
so. I worry about getting too much and I worry about
imbalances. They put in more of the things that are
inexpensive, like B vitamins and things with consumer
appeal like vitamin C. The formulas are based on market
forces, not nutritional needs."
Others decided against taking the pills.
Dr. Kava, of the
American Council on Science and Health, said she abstained.
"People ask me what vitamins I take," she said. "I say I
don't take any. They look at me askance. They can't believe
I'm a nutritionist."
Dr. Caballero also does not take vitamins. "There is no
disease I know of that is prevented by multivitamins," he
said.
In fact, Dr. Caballero said, typical pills, which contain a
variety of minerals as well as vitamins, have ingredients
that actually cancel out one another. "Minerals antagonize
each other for absorption," he said. "Zinc competes with
iron which competes with calcium."
Dr. Caballero also notes that large, rigorous studies that
were supposed to show that individual vitamins prevented
disease ended up showing the opposite. Those who took the
vitamins actually had more of the disease it was meant to
prevent.
Two large randomized trials of vitamin A and beta carotene
that researchers hoped would show a protective value
against cancer found no benefit, and one found that
participants who took the supplements had more cancer.
A large study of vitamin E and heart disease found that it
did not prevent heart attacks and that people taking it had
more strokes.
Another study, of women with heart disease, found that
antioxidant vitamins might actually increase the rate of
atherosclerosis.
Dr. Caballero said people were deluding themselves if they
thought multivitamins could make up for poor diets.
"If you eat junk food every day, vitamins are the least of
your problems," he said. "You cannot replace a healthy
diet. We don't know what ingredient in a healthy diet is
responsible for which condition. We do know that people who
consume five servings or more of fruits and vegetables have
less disease. But we don't know which ingredient. We tried
beta carotene, vitamin E and antioxidants, and they didn't
work.
"People are looking for the magic bullet. It does not
exist."
http://www.nytimes.com/2003/04/29/health/nutrition/29VITA.html?ex=1052829234&ei=\
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