Cologne, Germany - Vitamin C does not protect against colds, according to Germany's Institute for Quality and Efficiency in Health Care (IQWiG).

IQWiG noted that some dietary supplements contained over a gram of vitamin C, or 10 times more than the recommended daily dose. Because the body cannot absorb such a large amount, most of the vitamin is excreted in the urine a few hours later.

IQWiG cited a review of placebo-controlled trials by the Cochrane Collaboration, an international healthcare information organization with headquarters in Britain. The trials involved a total of more than 11,000 participants who ingested at least 0.2 grams of vitamin C per
day.

Participants who began taking the high doses of vitamin C after catching a cold noticed no difference in the duration or severity of their illness. For test persons who had been taking the high doses daily before getting ill, the duration of their colds was reduced by less than
one day per year.

The IQWiG warned that large amounts of vitamin C could cause diarrhoea, a potential problem especially for children and the elderly. (dpa)