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Vitamin

Vitamin C

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

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

What the research supports. 2 graded claims. Strongest: Improves iron absorption from plant foods (strong).

How much to take. Typical dose: 200–500 mg. Divided doses.

Side effects and interactions. 1 medication interaction listed. Serious: Kidney stones in predisposed (>2 g/d).

Stacking. Pairs well with Iron, Vitamin E.

Common forms. Available as Ascorbic acid, Sodium ascorbate, Liposomal, Ester-C.

Key studies. 9 studies cited. The strongest are listed with links to PubMed.

Community. Experiences from people who have tried Vitamin C. Anecdotes are not medical advice.

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

Molecular structureC6H8O6 · 176.12 g/mol

What it is

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

Also called

Ascorbic acidAscorbate

Food sources

CitrusBell pepperKiwiAcerola

Goals

Immune FunctionSkin, Hair & NailsGeneral WellnessHealthy Aging

How it works

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

  • +Collagen synthesis supports
  • ↑Non-heme iron absorption increases

What the research supports

Improves iron absorption from plant foodsstrong
Shortens common cold duration (~8% adults, ~14% kids)moderate

Strong: consistent results across large trials or meta-analyses. Moderate: several trials, mostly positive. Limited: small or mixed studies. Preclinical: animal or cell research only.

Typical dose
200–500 mg
TimingDivided doses
With foodWith a meal containing fat for fat-soluble compounds; otherwise either.
Best formMost evidence is based on the ascorbic acid form.
Upper limit2,000 mg
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Side effects & interactions

Common side effects

  • GI upset >2 g

Serious

  • Kidney stones in predisposed (>2 g/d)

Medication interactions

Iron supplementsminor

Beneficial — enhances absorption.

Check any supplement–medication combination with your pharmacist before starting.

Combines with

Pairs well

  • IronBoosts non-heme iron absorption.
  • Vitamin ERegenerates oxidized α-tocopherol.

Common forms

  • Ascorbic acid
  • Sodium ascorbate
  • Liposomal
  • Ester-C

Key studies

9 studies cited in total.

PubMed: Vitamin C — Shortens common cold duration ↗
Systematic review · PubMed (NLM) · 2026

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.

PubMed: Vitamin C — Improves iron absorption from plant foods ↗
Systematic review · PubMed (NLM) · 2026

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.

PubMed: Vitamin C — randomized controlled trial ↗
Systematic review · PubMed (NLM) · 2026

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

Discussion

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