Taking megadoses of vitamin C generally poses no danger, says Dr. Charles E. Butterworth, professor emeritus at the University of Alabama.
After a recent review of the evidence, he pronounced vitamin C "safe," even at high doses taken for long periods. He cites eight good studies showing no serious adverse effects from taking up to 10,000 milligrams a day of vitamin C for several years.
In fact, vitamin C has had a bad rap. Many of the rumors about vitamin-C toxicity are untrue, says Butterworth. For example, the evidence shows that:
High doses of vitamin C do not increase the risk of kidney stones.
Large doses of vitamin C do not destroy vitamin B-12.
Vitamin C does not cause cancer-causing mutations in cells.
High doses of vitamin C do not cause "iron overload" -- harmful accumulations of iron that accumulate in tissue -- in normal people. However, vitamin-C supplements may exacerbate iron toxicity in those with genetic defects in handling iron, notably a condition called hemochromatosis. In such cases, consult a doctor before taking vitamin-C supplements, he advises.
-- Jean Carper
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