Zinc vs Vitamin C
for cold prevention
Stronger evidence: Zinc
Stronger effect: Zinc
Safety: No notable interactions recorded for either.
For cold prevention, Zinc has the stronger evidence grade.
Zinc
grade B moderate certainty
zinc lozenges started early may modestly shorten cold duration
75+ mg/day at onset, lozenge
Vitamin C
studied, no effect moderate certainty
no reduction in cold incidence in the general population
sources: PMID:00000023 · PMID:00000008