- (CNN) - Researchers at the National Institutes
of Health are recommending doubling the adult daily allowance of vitamin
- Close to 40 percent of Americans consume
less than the current recommended daily allowance (RDA) of 60 milligrams
of vitamin C. In this week's Journal of the American Medical Association
(JAMA), the NIH said the RDA should be boosted to between 100 and 200 milligrams.
- The recommendation was last revised in
1989, and according to NIH's Dr. Mark Levine, "There has been a wealth
of new data" since then.
- Studies show people who eat at least
five servings a day of fruits and vegetables -- foods high in vitamin
C -- are at lower risk for certain cancers.
- "Cancer is a decades-long process,
and nutrition is one way of being able to thwart each step of the cancer
process," said Dr. Mitch Gaynor of Strang Cancer Prevention Center.
- NIH researchers said vitamin C should
come from food rather than supplements.
- A grapefruit and a cup of strawberries
contain almost 200 milligrams of the antioxidant. It also can be found
in papayas, kiwis, oranges and cantaloupe.
- Vegetables rich in vitamin C are peppers,
broccoli and kale, but they should be microwaved or steamed -- boiling
can destroy up to 80 percent of the vitamin.
- The NIH researchers said only those who
cannot eat produce should consider taking a 200 milligram supplement of
vitamin C. Taking 1000 or more milligrams can cause nausea and kidney stones
and will not prevent colds, they said.
- "We believe the evidence now, all
of it, suggests the only people who benefit from vitamin C when they have
colds are those who were deficient in the first place," Levine said.
- With this new research in hand, a government
recommendation for increased vitamin C intake is expected within the year.