Micronutrient | Subgroup | Effect on occurrence of infection | Effect on duration of symptoms | ||
RR (95% CI) | P value | Percent diff (95% CI) | P value | ||
Zinc | Main | 1.06 (0.95 to 1.18) | 0.31 | −47 (−73 to –21) | 0.0004 |
Common cold outcome* | 1.06 (0.95 to 1.18) | 0.31 | −59 (−84 to –35) | <0.0001 | |
Dose, mg/day | |||||
≤13.3 | Not est | −36 (−60 to –13) | 0.79 | ||
>13.3 | Not est | −43 (−81 to –4) | |||
Form of supplement | |||||
Gluconate | Not est | −251 (−396 to –106) | 0.76 | ||
Acetate | Not est | −206 (−462 to 30) | |||
Sex | |||||
Female | 1.31 (0.36 to 4.82) | 0.74 | −183 (−552 to 186) | 0.87 | |
Male | 0.81 (0.16 to 4.04) | −238 (−543 to 67) | |||
Continent | |||||
Africa | NR | 0.75 | NR | 0.023 | |
Asia | NR | NR | |||
Australia | NR | 440 (−160 to 1040) | |||
Europe | 0.89 (0.45 to 1.75) | NR | |||
North America | 1.06 (0.95 to 1.19) | −268 (−384 to –153) | |||
South America | NR | NR | |||
Length of trial | |||||
<2 weeks | 1.06 (0.94 to 1.20) | 0.92 | Not est | ||
2 weeks to <3 months | 1.05 (0.88 to 1.25) | ||||
3 months to <1 years | 1.02 (0.47 to 2.18) | ||||
>1 years | NR |
NR: Not relevant; that is, no primary studies that met the criteria. The mean age for all included studies was <40 years.
Not est: Not estimated; that is meta-analysis was not done.
*Sensitivity analysis.