According to research published in Annals of Internal Medicine (August 15, 2000;133:245–252, 302), zinc lozenges may shorten the duration of the common cold. The study involved 50 participants who began treatment within 24 hours of symptom onset. Subjects were randomly assigned to take either a zinc acetate lozenge containing 12.8 mg of elemental zinc or a placebo every two to three hours while awake, for as long as symptoms persisted.
Participants in the zinc group reported cold symptoms for an average of 4.5 days, compared to 8 days in the placebo group. Symptom severity was tracked for sore throat, sneezing, fever, runny nose, nasal congestion, cough, hoarseness, headache, and muscle aches. Runny nose and cough appeared to respond most consistently to zinc supplementation.
Reported side effects in the zinc group included dry mouth and constipation. The study was funded by a company that manufactures zinc lozenges, a fact that should be kept in mind when interpreting the findings.
Importantly, zinc does not “treat” a cold virus itself. Rather, zinc is an essential nutrient for immune function. If an individual is zinc deficient, supplementation can improve immune response, which may explain why some people experience shorter or milder colds when taking zinc. Because mild zinc deficiency is relatively common, many cold sufferers may benefit. In individuals who are not zinc deficient, however, supplementation is less likely to have a meaningful effect.
