Vitamin C: Complete Guide
Essential antioxidant that supports immune function, collagen synthesis, and iron absorption. Most people get enough from food, but supplementation helps during illness and high stress.
Quick Summary
Essential antioxidant that supports immune function, collagen synthesis, and iron absorption. Most people get enough from food, but supplementation helps during illness and high stress. 500-1,000mg daily for general supplementation. Best form: Ascorbic Acid.
What is Vitamin C?
Vitamin C (ascorbic acid) is a water-soluble vitamin your body can't produce or store. It's involved in immune defense, collagen production (skin, joints, blood vessels), wound healing, and acts as a powerful antioxidant. Unlike fat-soluble vitamins, excess vitamin C is excreted in urine, so toxicity is rare.
Who Should Consider Vitamin C?
- People who get frequent colds or infections
- Smokers (need 35mg more daily than non-smokers)
- Those with high stress levels (cortisol depletes vitamin C)
- People recovering from surgery or wounds
- Those who eat very few fruits and vegetables
- Iron-deficient individuals (vitamin C improves absorption)
How It Works
Vitamin C donates electrons to neutralize free radicals (antioxidant action), serves as a cofactor for enzymes that build collagen, enhances iron absorption in the gut by converting ferric iron to ferrous form, and supports immune cells including neutrophils and lymphocytes. During infection, immune cells accumulate vitamin C at concentrations 100x higher than blood plasma.
Forms Comparison
Different forms of Vitamin C have varying absorption rates and best uses. Here's how they compare:
| Form | Bioavailability | Best For |
|---|---|---|
| Ascorbic Acid | 70-90% | Most people. Cheap, well-absorbed, well-studied. |
| Sodium Ascorbate | 70-90% | Sensitive stomachs. Buffered form, less acidic. |
| Liposomal Vitamin C | 90%+ | Higher doses without GI upset. Premium option. |
| Ester-C | 70-90% | Marketing claims outpace evidence. Works but not superior. |
Our recommendation: Ascorbic Acid for most people due to superior absorption and tolerability.
Benefits & Evidence
Vitamin C has 3 strongly-evidenced benefits and 2 moderately-evidenced benefits.
Immune support during illness
strong evidence29 RCTs: reduces cold duration by 8% in adults, 14% in children
Collagen synthesis for skin
strong evidenceEssential cofactor. Deficiency causes scurvy (collagen breakdown)
Iron absorption enhancement
strong evidence67% improvement in non-heme iron absorption when taken together
Antioxidant protection
moderate evidenceReduces oxidative stress markers in clinical trials
Blood pressure reduction
moderate evidenceMeta-analysis: 500mg/day reduces systolic BP by 3.8 mmHg
Dosing & Timing
Recommended Doses
Timing
Side Effects & Interactions
Possible Side Effects
- GI upset at high doses. Common above 2,000mg
- Kidney stones (very rare). Only with chronic megadoses
Interactions to Know
- Enhances iron absorption (beneficial for iron-deficient, caution with hemochromatosis)
- May affect blood sugar readings on glucometers
- High doses may interact with blood thinners (warfarin)
Frequently Asked Questions
Not really. Regular supplementation reduces duration by 8% but doesn't prevent infection. Exception: 1-2g before extreme physical stress (marathon, military training) does reduce incidence by 50%.
Ingredient Analysis Pages
Full evidence-based analysis for each form and variant:
Related Topics
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About this information: Our analysis of Vitamin C is based on peer-reviewed research from PubMed, ClinicalTrials.gov, and NIH databases. These statements have not been evaluated by the FDA. Supplements are not intended to diagnose, treat, cure, or prevent any disease.
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