Zinc Gluconate and the Common Cold: A Controlled Clinical Study

Abstract

A report in 1984 on the success of zinc gluconate against common cold symptoms could not be confirmed in three subsequent studies, which are now known to have used formulations that inactivated zinc. A non-chelating formulation including glycine, which releases 93% of contained zinc into saliva, was tested in a randomized, placebo-controlled, double-blind trial in 73 young adults. Efficacy was recorded in symptom diaries using a symptom severity rating. Patients' symptoms first appeared 1.34 days prior to entry to the study in both groups. Disappearance of symptoms occurred after an additional 4.9 days for zinc-treated patients versus 6.1 days for placebo-treated patients. A difference was noted in the efficacy of treatment if it was started 1 day after symptom onset: cold duration was an additional 4.3 days in zinc-treated patients compared with 9.2 days for placebo-treated patients. Cough, nasal drainage and congestion were the symptoms most affected, and only mild side-effects were noted.

Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials

“…30 Other bias was unclear in three trials. 30,34,35 Sensitivity analysis excluding these trials did not change the results, so the evidence was not downgraded. b Serious inconsistency: Very high statistical heterogeneity (I 2 = 95%).…”

“…Zinc may also reduce the severity of cold symptoms by acting as an astringent on the trigeminal nerve. 9,10 A recent meta-analysis of randomized controlled trials concluded that zinc was effective at reducing the duration and severity of common cold symptoms. 11 However, there was considerable heterogeneity reported for the primary outcome (I 2 = 93%), and subgroup analyses to explore betweenstudy variations were not performed.…”

“…31,35 One trial did not describe random sequence generation, 35 and two trials had unclear selective reporting bias. 30,35 One trial had incomplete outcome data. 30 Other bias was unclear in three trials.…”

“…30,35 One trial had incomplete outcome data. 30 Other bias was unclear in three trials. 30,34,35 Sensitivity analysis excluding these trials did not change the results, so the evidence was not downgraded.…”

Viral Respiratory Tract Infections in Cystic Fibrosis

“…Zinc lozenges appeared to have positive effects on adults but negative effects on children in terms of duration and severity of common cold symptoms (Macknin, Piedmonte et al 1998;Marshall 2000). Higher doses were found to have a greater impact in reduction of symptom duration and reduced symptom severity (Godfrey, Conant Sloane et al 1992;Mossad, Macknin et al 1996). Zinc nasal spray appears to reduce the total symptom score but has no effect on the duration of common cold (Belongia, Berg et al 2001).…”