Posted on March 31, 2008 in Latest News
High Doses of Vitamin C May be Harmful Any vitamin in excess does more harm than good. Findings from the researchers at the Duke University Medical Centre contradict an epidemiologic study that suggested vitamin C might protect against osteoarthritis, said lead investigator, Virginia Kraus. In the Duke study, the researchers fed guinea pigs with low, medium and high doses of vitamin C. According to the scientists the pigs develop knee osteoarthritis in a manner similar to humans.
The researchers found that high-dose guinea pigs developed more cartilage damage and had more bony spurs form in their knee joints than did the medium- and low-dose groups. The researchers found an important protein in bone growth called active transforming growth factor beta almost exclusively in the osteophytes. The protein is known to cause joint degeneration and spur formation, and vitamin C can convert this protein from an inactive to an active state, Kraus said. This conversion means that vitamin C’s ability to enhance collagen synthesis and activate transforming growth factor beta might be the reason guinea pigs fed high doses of vitamin C developed more osteoarthritis, she added.
Dr. Ian D. Podmore and colleagues from the University of Leicester, UK, report that vitamin C may have a deleterious effect when taken in daily doses of 500 milligrams (mg). Their findings follow a trial of 30 healthy volunteers who were given doses of 500 mg — or about eight times the UK recommended daily allowance — for a period of 6 weeks. In the April 9th issue of the journal Nature, the researchers report that at a dose of 500 mg/day vitamin C has both a damaging pro-oxidant as well as a beneficial antioxidant effect on two important markers of molecular damage, 8-oxoguanine and 8-oxoadenine.
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