For so long, it seemed so easy.
Vitamins were good for you, so why not pop a daily
pill, an easy-to-swallow insurance policy against
colds or more serious diseases such as cancer or
heart disease?
But a growing
number of experts are warning that generally
healthy people may be overdoing it on vitamin
supplements -- particularly vitamins A, E and C --
especially in combination with a healthy diet that
contains fortified foods such as milk or cereals.
There is no proof that taking vitamin pills offers
protection against any disease, but there is some
evidence that in some cases, supplements may
actually increase the risk of getting cancer or
osteoporosis.
"I don't think you should arbitrarily take a
supplement. If you are eating a healthy
well-balanced diet and consuming food from all
four food groups, you need to question whether you
need to take a multi-vitamin," says Theresa
Glanville, an associate professor in the
department of applied human nutrition at Mount
Saint Vincent University in Nova Scotia. She
doesn't take vitamins.
It has been well established for years that a
deficiency in a particular vitamin can cause
illness. A lack of Vitamin D, for example, can
cause rickets, a softening and weakening of the
bones. Too little Vitamin C leads to scurvy.
It has also been known for years that large
amounts of some vitamins can be toxic.
Vitamin consumption began rising during the
1950s and '60s, which brought exciting findings
that indicated some vitamins might actually
protect against cancer and other diseases.
Vitamins C and E and beta-carotene are
antioxidants that help the body deal with free
radicals. Free radicals occur when our bodies use
oxygen, and they damage cells the same way rust
damages a car. Antioxidants stop free radicals
from forming and bind with those already in the
body to prevent the cellular "rusting" that can
lead to cancer and other illnesses.
Many doctors and nutritionists began
recommending that people take vitamin supplements,
reasoning that moderate amounts of vitamins don't
do any harm and may be good preventive medicine.
But proof of that proved elusive. Study after
study has failed to find that vitamin supplements
reduce the risk of disease.
What the research has found, however, is that
vitamin A, E and C supplements could increase the
risk of some health problems.
Last week, a U.S. team of researchers found
that taking 25 milligrams a day of beta-carotene,
a precursor to vitamin A, increases the risk of
colon cancer in people who smoke and consume at
least one alcoholic drink a day. Many
multi-vitamin pills in Canada contain at least
this much beta-carotene.
Studies have suggested that too much vitamin A
can reduce bone density, which increases the risk
of osteoporosis. In high levels, it can also cause
birth defects.
There is some evidence that taking vitamin E
can increase the risk of stroke in women, and that
too much vitamin C can cause digestive problems,
including nausea, abdominal pain, flatulence and
diarrhea.
How much is too much? It depends on the
vitamins you take, and your diet.
Since the early 1990s, Canadian and U.S.
dietary experts have worked together, through the
National Academy of Sciences in the United States,
to evaluate the existing research on vitamins and
minerals. They determined a healthy range of
vitamin consumption, but they also took a new
approach and set a safe upper limit -- defining
for the first time how much may be too much.
The upper-limit guidelines are part of a new
way of looking at vitamins that Health Canada is
planning to adopt.
In the United States, a growing number of
doctors and medical researchers are worrying that
people are taking more vitamins than is good for
them, according to a recent article in The New
York Times.
Canadian researchers share the concerns about
overuse, but say the situation in Canada may not
be exactly the same. Americans may be ingesting
more vitamins than Canadians, says Dr. Katherine
Gray-Donald, director of the school of dietetics
and human health at McGill University in Montreal.
That is because more of their food is fortified
with vitamins and other nutrients -- and in some
cases to a greater degree -- than in Canada.
"I brought home a box of cereal from the U.S.
and it had the daily recommended intake of calcium
in one bowl," she said. "When my husband took a
second bowl, I told him, "You can't have two bowls
of that cereal." (Too much calcium may lead to
kidney stones.)
Health Canada has a more conservative approach
to fortifying foods than the United States, and
some critics have called it overly restrictive.
Canadian milk is fortified with Vitamin D. Salt is
fortified with iodine. In cases where nutrients
are removed from food during processing -- for
example, some of the vitamins, iron and folic acid
that occur naturally in flour -- manufacturers are
allowed to put them back. Vitamin A can be added
to margarine so it can compete nutritionally with
butter.
But food manufacturers are not permitted to add
vitamins to any product they see fit.
That approach is now under review. Health
Minister Anne McLellan announced last week that
Canada will give food manufacturers more
discretion in terms of which products can include
extra vitamins. Exactly how the new system will
work is still unclear. Consultations will take
place in Ottawa at the end of the month. No
decisions will be made on approving new products
until the fall.
There is a heated debate among experts over
whether inexpensive but popular foods such as
chips or pop should be fortified with vitamins.
This would improve the diets of low-income
Canadians who can't afford the fruits and
vegetables needed for a healthy diet, says Harvey
Anderson, a professor of nutritional science at
the University of Toronto.
Canadians who eat a healthy diet and take
vitamins tend to be well educated and have higher
incomes, he says. He is worried the government
will not allow companies to add vitamins to more
food products for fear that higher-income
Canadians will end up with an overloaded diet,
according to the new safe upper limits for
vitamins.
He also says the science on which those new
limits are based is questionable.
"You are ignoring the people who are at risk of
having inadequate intake. In a sense, it is
protecting the rich and foolish at the expense of
the poor. To me, public health means you look at
both ends of the spectrum," Dr. Anderson says.
Karen Dodds, director-general of Health
Canada's food directorate, says research is under
way to see if there is a nutrition gap in Canada,
but the current evidence suggests there isn't one,
at least as far as vitamins and minerals are
concerned. "We don't see population deficiencies
in vitamins and minerals."
She also says she hasn't seen any evidence that
shows Canadians are overdoing it on vitamins and
minerals.
There is some evidence, however. Dr.
Gray-Donald recently published a study that found
Canadians were taking in too much niacin, a B
vitamin many people take to lower the risk of
heart disease. The safe daily upper limit is 35
mg, and some multi-vitamins have 50.
Taking too much doesn't cause serious health
problems, but it can cause flushing, which can
send people to their doctor worried they are
suffering from something more serious.
Her survey of Canadians didn't find more
serious vitamin overdoses, although it asked only
about vitamin pills or supplements that people had
taken in the past 24 hours. A survey that asked
about weekly habits might have produced different
results, she says.
No one is saying Canadians should stop taking
vitamins, which offer a variety of health
benefits. Folic acid, taken before a woman gets
pregnant and in the first few months after
conception, has been proved to reduce birth
defects such as spina bifida.
There are also tantalizing signs --
circumstantial evidence -- of the good they may do
in preventing disease.
"We still need proof, but there are many signs
that B vitamins are good for the heart," says
David Spence at the Robarts Research Institute in
London, Ont. He believes in taking supplements, at
least of the B vitamins.
Researchers have found that vitamins B-6 and
B-12 can reduce levels of a naturally occurring
chemical called homocysteine, which damages the
lining of the arteries. People with high levels of
homocysteine are at greater risk for heart attack
and stroke.
But two large studies found no evidence that
B-6 and B-12 reduce the incidence of heart attack
and stroke.
Dr. Spence believes that proof the B vitamins
help to prevent heart disease will soon
materialize, and in the meantime, he takes them
regularly.
Other experts, like Dr. Glanville, say that, in
general, it's better to get your vitamins through
a balanced diet. Plenty of studies show that a
diet rich in veggies and fruit reduces the risk of
getting cancer or heart disease. This probably
means that more than just the vitamins in food
help prevent disease.
"A tomato on the vine produces all kind of
chemicals that protect it in a harsh environment.
When we eat it, some of that protective effect is
being transferred to us."
Anne McIlroy is The Globe and Mail's science
reporter.
Vitamin ABCs:
VITAMIN A
How much do adults need?
900 micrograms a day for men and 700 for women
How much may be too much?
3,000 micrograms a day for both men and women
Food sources
Orange fruits and vegetables such as squash,
pumpkin, carrots, sweet potatoes and mango;
vegetables with dark green leaves such as spinach
and broccoli; liver
Amounts found in typical servings
Three spears of raw broccoli: 462 micrograms;
one green pepper: 189 micrograms
What it does
It's important for a healthy immune system and
for good vision
VITAMIN C
How much do adults need?
90 milligrams a day for men, 75 milligrams a
day for women
How much may be too much?
2,000 milligrams a day
Foods sources
Citrus fruits such as orange and grapefruit,
strawberries, tomatoes, papaya; red and green
peppers and spinach
Amounts found in typical servings
One orange: 53 mg; one red pepper: 190 mg
What it does
It is an antioxidant that protects against the
damage caused by free radicals
VITAMIN E
How much do adults need?
15 milligrams a day
How much is too much?
1,000 mg a day
Food sources
Almonds, walnuts, wheat germ, avocado, whole
grains, corn oil, sunflower seeds
Amounts found in typical servings
One ounce of almonds: 7.5 mg; two tablespoons
of peanut butter: 3.2 mg
What it does
It is an antioxidant
Who takes vitamins?
Income, education and gender are key factors.
Sixty-six per cent of Canadians with university
degrees take vitamins, compared to 53 per cent
with a high school diploma or lower.
In homes with a household income of $70,000 or
more, 64 per cent take vitamins. When income is
less than $35,000, the figure drops to 56 per
cent.
Percentage of men
who take vitamins:
50
Percentage of women:
67
Sources: The Recommended Intakes for
Individuals and the Tolerable Upper Intake Levels,
The National Academy of Sciences (recommended
intakes vary for children, for pregnant and
lactating women, and for the elderly).
Gerry Harrington, the Nonprescription Drug
Manufacturers Association of Canada.
