Vitamin C and acute illness in Navajo schoolchildren.

To evaluate earlier observations, including our own, showing usefulness of vitamin C for managing the common cold, we performed a double-blind trial of vitamin C versus placebo in 868 children. There was no difference in number becoming ill (133 versus 129), number of episodes (166 versus 159) or mean illness duration (5.5 versus 5.8 days) between the groups. Children receiving vitamin C had fewer throat cultures yielding beta-hemolytic streptococcus (six versus 13, P less than 0.10), but no difference in overall complicated illness rate (24 versus 25). Plasma ascorbic acid levels were higher in the vitamin group 24 to 26 hours after supplementation (1.28 versus 1.04 mg per 100 ml, P less than 0.01). Children with high plasma ascorbic acid concentrations had longer mean illness (6.8 versus 4.0 days, P less than 0.05) than those with low levels. Vitamin C does not seem to be an effective prophylactic or therapeutic agent for upper respiratory illness.