Outcome
    Moderate Evidence
    Effectiveness 3/5

    Vitamin C for Antioxidant Protection

    Get to sufficiency, then stop. Antioxidant "more is better" thinking has repeatedly failed in trials.

    Overview

    Get to sufficiency, then stop. Antioxidant "more is better" thinking has repeatedly failed in trials.

    Verdict

    Mixed evidence

    Vitamin C is the body's primary water-soluble antioxidant and regenerates vitamin E — but supplementing above repletion does not improve health outcomes.

    How It Works

    Ascorbate donates electrons to quench superoxide, hydroxyl and peroxyl radicals in the aqueous phase, and reduces the tocopheryl radical back to active vitamin E at the membrane interface, effectively recycling lipid-phase antioxidant capacity. It is also a cofactor for dioxygenase enzymes involved in collagen and carnitine synthesis.

    Dosing & Protocol

    Typical dose

    Recommended dose
    200 mg daily saturates plasma and tissue in most adults. Higher intakes are largely excreted.
    Expected timeframe
    Plasma saturates within days to weeks.

    Protocol

    dose
    200 mg daily
    form
    Ascorbic acid or food sources
    note
    Five servings of fruit and vegetables typically supply 200 mg without a supplement
    timing
    With food
    duration
    Ongoing

    Evidence

    What the studies say

    Biochemical antioxidant activity is unambiguous, and plasma markers of oxidative damage fall with repletion. However, large randomised trials of antioxidant supplementation have not reduced cardiovascular events or cancer incidence, and high-dose antioxidants can blunt the training adaptations that exercise-induced oxidative signalling drives. The clinical value is in avoiding deficiency, not in maximising intake.

    Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

    Score: 9/10
    2012
    meta_analysis
    n=296707

    Bjelakovic G, Nikolova D, Gluud LL +2 more

    vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07)

    View source

    Vitamin C and immune function

    Score: 8/10
    2017
    systematic_review

    Carr AC, Maggini S

    Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system.

    View source

    The roles of vitamin C in skin health

    Score: 7/10
    2017
    systematic_review

    Pullar JM, Carr AC, Vissers MCM

    Normal skin contains high concentrations of vitamin C, which supports important and well-known functions, stimulating collagen synthesis and assisting in antioxidant protection against UV-induced photodamage.

    View source

    Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial

    Score: 10/10
    2008
    rct
    n=14641

    Sesso HD, Buring JE, Christen WG +7 more

    There also was no significant effect of vitamin C on major cardiovascular events.

    View source

    Safety

    Caveats

    Do not take high-dose vitamin C around resistance or endurance training — it can attenuate mitochondrial and hypertrophic adaptation. Above 1 g, vitamin C can act as a pro-oxidant in the presence of free iron. Vitamin C is a proven antioxidant biochemically, but the largest long-term trial (Physicians' Health Study II, n=14,641, 8 years) found no reduction in cardiovascular events, so antioxidant activity has not translated into hard clinical outcomes in well-nourished people.

    Less likely to help if

    Anyone already eating a produce-rich diet will gain little.

    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.