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evidence · mechanism · dose
Supplements/Vitamin

Vitamin C

aka Ascorbic acid · Ascorbate

Water-soluble antioxidant, collagen cofactor, and immune supporter.

Immune FunctionSkin, Hair & NailsGeneral WellnessHealthy Aging

Overview

Water-soluble antioxidant, collagen cofactor, and immune supporter.

Natural sources
  • Citrus
  • Bell pepper
  • Kiwi
  • Acerola
Common forms
  • Ascorbic acid
  • Sodium ascorbate
  • Liposomal
  • Ester-C

Mechanism of action

Reducing agent; cofactor for prolyl/lysyl hydroxylase (collagen) and dopamine β-hydroxylase.

Pathways
  • · Collagen hydroxylation
  • · Iron absorption (non-heme)
  • · Antioxidant recycling (regenerates vit E)

Effects on the body

Supports
Collagen synthesis
Increases
Non-heme iron absorption

Organ system effects

Skin

Required for collagen crosslinking.

Immune System

Concentrated in neutrophils.

Evidence-based benefits

Shortens common cold duration (~8% adults, ~14% kids)

Moderate evidence

Improves iron absorption from plant foods

Strong evidence

Potential side effects

Common
  • · GI upset >2 g
Rare
    Serious
    • · Kidney stones in predisposed (>2 g/d)

    Drug interactions

    Iron supplements
    Beneficial — enhances absorption.
    minor

    Safety & non-supplemental interactions

    Educational summary — always confirm with your clinician or pharmacist before starting, stopping, or combining with prescription therapy.

    Avoid with these conditions
    • ·Autoimmune disease (theoretical immune activation)
    Avoid / monitor with these medications
    • ·Immunosuppressants

    Supplement interactions

    Pairs well with
    • Iron
      Boosts non-heme iron absorption.
    • Vitamin E
      Regenerates oxidized α-tocopherol.
    Avoid combining with

    No specific avoidances listed.

    Dosing & bioavailability

    Typical dose
    200–500 mg
    Upper safe limit
    2,000 mg
    Timing
    Divided doses

    Where to buy

    Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

    Vitamin
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    Amazon
    Wide selection · fast shipping
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    iHerb
    Global delivery · curated brands
    Vitamin
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    Thorne
    Practitioner-grade · NSF tested

    Scientific evidence (9)

    Systematic reviewExamine.com Supplement Database · 2023

    Vitamin C: pharmacology, clinical evidence, and safety — narrative review

    Examine.com Research Team

    Curated narrative review of human and preclinical evidence for Vitamin C, including mechanism, typical dosing, and safety considerations.

    Key findings

    Best-supported outcome: Shortens common cold duration (~8% adults, ~14% kids) (evidence: moderate). Additional outcomes and limitations summarized in the full profile.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — Shortens common cold duration

    Live PubMed search

    Live results for "Vitamin C Shortens common cold duration" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "Shortens common cold duration". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — Improves iron absorption from plant foods

    Live PubMed search

    Live results for "Vitamin C Improves iron absorption from plant foods" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "Improves iron absorption from plant foods". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — randomized controlled trial

    Live PubMed search

    Live results for "Vitamin C randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — meta-analysis

    Live PubMed search

    Live results for "Vitamin C meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — pharmacokinetics

    Live PubMed search

    Live results for "Vitamin C pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — safety adverse events

    Live PubMed search

    Live results for "Vitamin C safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Vitamin C — dose response

    Live PubMed search

    Live results for "Vitamin C dose response" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Vitamin C and "dose response". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewGoogle Scholar · 1970

    Google Scholar: Vitamin C — clinical evidence

    Live Scholar search

    Cross-database citation index for Vitamin C as it relates to "clinical evidence".

    Key findings

    Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

    Open study
    Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.