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Immunity / Common Cold (URTI) Support

Adults seeking evidence-based adjuncts; NOT a substitute for vaccination/medical care.

immunity

URTI

reduce risk (limited) and/or duration of URTI

Core stack

Vitamin D (status-based)

B → C (updated evidence mixed)

Dose: 1000–2000 IU/day (or per clinician to correct deficiency)

Daily with fat-containing meal

Ongoing during low-sun months

Why: Earlier IPD meta-analysis suggested modest protection; recent updates show attenuated/neutral effects overall—benefit most plausible in deficient individuals.

Sources

Adjuncts

Zinc lozenges (acetate/gluconate)

Dose: 75–90 mg elemental/day divided (onset of symptoms)

Start within 24 h of cold symptoms; limit to ≤14 days

Notes: May shorten duration by ~2 days; taste/GI side-effects common; avoid intranasal zinc.

Sources

Cochrane (2024) summary

Probiotics (selected strains)

B (low–moderate certainty overall)

Dose: 1–10 billion CFU/day (strain-dependent)

Notes: Some strains reduce risk and/or shorten URTIs; effects are strain- and context-specific.

Sources

Not recommended

Megadose vitamin C/Echinacea for prevention: Heterogeneous/weak evidence; side-effects possible.

Monitoring

Adverse effects (nausea, taste changes)
Total daily zinc to avoid copper deficiency with prolonged use