Colds and infections
Catching colds, flu and other common infections, and how long they last.
14 findings across 5 topics. Strongest evidence: Zinc (A), Vitamin C (B), Honey (C).
Grades show how certain the evidence is, not how big the effect is. How we grade evidence
What helps
Zinc
- Reduces diarrhea and infection risk in deficiency — Benefit, grade A: Strong
- Shortens common cold duration — Benefit, grade B: Moderate
Vitamin C
- Eases cold symptoms — Benefit, grade B: Moderate
- Prevents colds during heavy physical stress — Benefit, grade B: Moderate
- Shortens colds when taken every day — Benefit, grade B: Moderate
Honey
- Eases acute cough in children — Benefit, grade C: Limited
- Eases cold symptoms overall — Benefit, grade C: Limited
Garlic
- Makes colds and flu milder — Benefit, grade C: Limited
Mixed evidence
Garlic
- Helps prevent colds — Mixed results, grade C: Limited
Doesn't seem to help
Vitamin C
- Prevents colds in the general population — No effect, grade B: Moderate
- Shortens a cold if you start it when symptoms begin — No effect, grade B: Moderate
Vitamin D
- Prevents colds and respiratory infections — No effect, grade B: Moderate
Zinc
- Prevents common colds — No effect, grade B: Moderate
Honey
- Shortens a cough in adults — No effect, grade C: Limited