Condition
    Effectiveness 2/5

    Vitamin C for Acute Bronchitis

    Vitamin C has one of the largest evidence bases in respiratory illness and one of the smallest effects. Regular supplementation modestly shortens illness duration but does not prevent infection in the general population.

    Overview

    Vitamin C has one of the largest evidence bases in respiratory illness and one of the smallest effects. Regular supplementation modestly shortens illness duration but does not prevent infection in the general population.

    Verdict

    Mixed evidence

    Regular vitamin C intake slightly shortens respiratory illness duration; starting it after symptoms begin does not reliably help.

    How It Works

    Vitamin C accumulates in neutrophils and supports phagocytic function and epithelial barrier integrity. Levels fall during infection, which is the rationale for supplementation, but repletion does not appear to alter infection risk.

    Dosing & Protocol

    Typical dose

    Recommended dose
    200 mg daily as regular intake; therapeutic doses started after onset show little benefit
    Expected timeframe
    Duration benefits accrue only with ongoing intake before illness begins

    Protocol

    notes
    Doses above 1 g daily commonly cause loose stools and increase oxalate kidney stone risk in susceptible people
    dosage
    200 mg daily taken regularly; higher doses offer no added duration benefit
    duration
    Ongoing daily intake rather than reactive dosing

    Evidence

    What the studies say

    Pooled trials show regular supplementation reduces cold duration by about 8% in adults and 14% in children — roughly half a day. Incidence is unchanged except in people under extreme physical stress (marathon runners, soldiers in subarctic conditions), where risk roughly halves. Therapeutic dosing begun after symptom onset shows inconsistent and generally null results.

    Vitamin C for preventing and treating the common cold

    Score: 9/10
    2013
    systematic_review
    n=11306

    Hemila H, Chalker E

    Regular vitamin C did not reduce cold incidence in the general population but shortened duration modestly

    View source

    Safety

    Caveats

    Effect size is small and not clinically dramatic. High-dose intake raises oxalate excretion and may increase kidney stone risk in predisposed individuals.

    Less likely to help if

    People who begin vitamin C only once the cough has started should not expect the duration benefit seen in regular-intake trials.

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.