Vitamin C
The essential antioxidant for immune defense, collagen synthesis, and iron absorption.
Also known as: Ascorbic Acid • L-Ascorbic Acid • Ascorbate
Overview
Vitamin C (ascorbic acid) is a water-soluble essential vitamin that humans cannot synthesize — we must obtain it from food or supplements. It serves as a powerful antioxidant, a critical cofactor for collagen synthesis, and a key player in immune function. While severe deficiency (scurvy) is rare in developed countries, suboptimal levels are common, particularly among smokers, the elderly, and those with limited fruit and vegetable intake.
Key Benefits
Immune System Support
Vitamin C supports both innate and adaptive immunity. It enhances neutrophil function, supports lymphocyte proliferation, and increases antibody production. Regular supplementation reduces cold duration by 8% in adults and 14% in children.
Powerful Antioxidant
As an electron donor, vitamin C neutralizes free radicals and reactive oxygen species. It also regenerates other antioxidants, including vitamin E, making it a cornerstone of the body's antioxidant defense network.
Collagen Production
Vitamin C is an essential cofactor for the enzymes prolyl hydroxylase and lysyl hydroxylase, which are required for collagen synthesis. Without adequate vitamin C, the body cannot produce stable collagen, affecting skin, joints, blood vessels, and wound healing.
Iron Absorption
Vitamin C enhances non-heme iron absorption by up to 67% by converting ferric iron to the more absorbable ferrous form. Taking vitamin C with iron-rich meals or iron supplements significantly improves iron status.
Dosage & How to Take
The RDA is 90mg for men and 75mg for women, but optimal supplemental doses are typically 500–2,000mg daily.
| Purpose | Dose | Notes |
|---|---|---|
| General health | 500–1,000 mg/day | Divided into 2 doses |
| Immune support | 1,000–2,000 mg/day | Increase during illness to 3,000–4,000 mg/day |
| Skin/collagen | 500–1,000 mg/day | Consistent daily intake is key |
| Iron absorption | 200–500 mg | Take with iron-containing meals |
Best Time to Take
Divide into 2–3 doses throughout the day for better absorption
With or Without Food
Can be taken with or without food; with food reduces GI upset at high doses
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| Ascorbic Acid | Good | General supplementation | Most studied form; may cause GI upset at high doses |
| Sodium Ascorbate | Good | Sensitive stomachs | Buffered form, less acidic, gentler on stomach |
| Liposomal Vitamin C | Excellent | Maximum absorption | Encapsulated in liposomes for superior absorption; more expensive |
| Ester-C (Calcium Ascorbate) | Good | Sensitive stomachs | pH-neutral, contains calcium; no evidence of superior efficacy |
Side Effects & Safety
Common
- GI discomfort at doses >2,000mg
- Diarrhea (osmotic effect at high doses)
- Nausea
Rare
- Kidney stones (in predisposed individuals at very high doses)
- Iron overload in hemochromatosis
Contraindications
- History of calcium oxalate kidney stones (use caution >1,000mg)
- Hemochromatosis
- G6PD deficiency (avoid IV vitamin C)
Interactions
Enhances iron absorption — beneficial interaction
May interfere with some chemo agents — consult oncologist
High doses may reduce warfarin effectiveness
Scientific Research
Vitamin C and Immune Function
Regular supplementation reduced cold duration by 8% in adults and 14% in children
Liposomal vs Standard Vitamin C
Liposomal delivery achieved 1.5x higher blood levels than standard ascorbic acid
Vitamin C and Collagen Synthesis
Vitamin C supplementation increased type I collagen synthesis by 8x in fibroblast cultures
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.