Source:
UPI Science News
CHICAGO,
April 20 (UPI) -- Take more vitamin C. But not too much. Federal
health experts are recommending increasing the daily dietary allowance
(RDA) of vitamin C to between 100 mg and 200 mg, from the current
RDA of 60 mg. But, the researchers, from the National Institutes
of Health in Bethesda, Md., say taking more than 1,000 mg (one
gram) a day can have adverse effects.
The
study about the role of vitamin C in the diet appears in Wednesday's
issue of The Journal of the American Medical Association (JAMA).
Dr. Mark Levine and his colleagues at the National Institutes
of Health in Bethesda, Md., wrote, ''Whenever possible, vitamin
C intake should come from fruits and vegetables and physicians
should encourage their patients to eat five servings of fruits
and vegetables daily.''
They
added, however, that ''Vitamin C doses of 1 gram or more could
have adverse consequences in some people, and physicians should
counsel patients to avoid these doses.'' ''The message here is
eat a variety of fruits and vegetables,'' Levine told UPI. ''We
don't know just yet if the protective effects come in the vegetables
or in the vitamin so we recommend you eat a wide variety of fruits.''
He listed vitamin C sources such as cantaloupe, grapefruit, kiwi,
honeydew, mangos and strawberries, and an assortment of vegetables
such as broccoli, Brussels sprouts, tomatoes, kale, baked potatoes,
snow peas, and sweet potato.
He
adds that if you eat your high-C fruits and vegetables, you don't
need to take a vitamin supplement. Supplements are only for people
who can't or won't eat fruits and vegetables. Some can't because
of gastrointestinal problems and these fruits and vegetable make
it worse. In that case, the researchers recommend supplements.
Vitamin
C, also known as ascorbic acid, is one of 13 essential vitamins,
chemicals that the body needs to function properly. The body doesn't
produce the vitamin naturally so people need to ingest the recommended
allowance in order to avoid diseases caused by a deficiency of
vitamin C. The current RDA for vitamin C _ 60 mg _ was set in
1980. The Food and Nutrition Board of the National Academy of
Sciences (NAS) is currently reviewing that recommendation.
Since
the last review in 1989, the article reports that new biochemical,
molecular, epidemiological and clinical data have become available.
''There's been an explosion in anti-oxidant research, including
vitamin C since 1989,'' says Levine. The researchers analyzed
that data, compared it to the current recommendations and came
up with the new dosage. He says that in 1989 there wasn't as much
information available on the body's functional dose of vitamin
C as there is now.
Today
they know that the body has to work hard to absorb more than 100
mg. ''At a certain amount, the body won't absorb any more,'' Dr.
Levine says. ''At about 200 milligrams the body fills up. By 500
milligrams a day, it absorbs only 70 percent, the rest is eliminated
by the kidneys. The body doesn't want anymore.'' Vitamin C is
a safe vitamin, he says, but adds that some patients can have
adverse effects. Patients with an iron overload or on dialysis,
for example, are at risk from suffering form a vitamin C overdose.
Plus, excreting more than one gram a day could result in kidney
stones.
''So
in a nutshell, don't take more than a gram of vitamin C and get
it from your diet,'' he says. What about people who take a high
dose of vitamin C to fight the common cold? ''From all the data
we studied, it only benefited people who were deficient in the
first place.'' The body excretes the amount it cannot use. The
report's recommendation of 200 mg from five servings of fruits
and vegetables daily are similar to those of U.S. Department of
Agriculture and National Cancer Institute, the article noted.
