Immunity/Inflammation/Beauty

Vitamin C

An essential water-soluble antioxidant vital for immune function, collagen synthesis, and iron absorption, with modest but consistent evidence for reducing cold duration and severity.

Vitamin C

An essential water-soluble antioxidant vital for immune function, collagen synthesis, and iron absorption, with modest but consistent evidence for reducing cold duration and severity.

score

evidence

Safe

risk

Proven Benefits

01Shortens common cold duration

02Reduces cold severity (especially severe symptoms)

03Essential cofactor for collagen synthesis

04Potent water-soluble antioxidant

05Enhances non-heme iron absorption

06Supports wound healing

07Halves cold incidence under extreme physical stress

Chemical Forms

Recommended

Ascorbic acid (most studied, cost-effective)
Sodium ascorbate (buffered, gentler on stomach)
Liposomal vitamin C (enhanced bioavailability)
Ascorbyl palmitate (fat-soluble form for skin)

Avoid

Mega-dose tablets >2,000 mg (poorly absorbed, GI distress)
Calcium ascorbate in kidney stone-prone individuals

Expert Note

Standard ascorbic acid is effective; buffered for sensitive stomachs

Protocol

Amount

200 mg - 1,000 mg

Frequency

daily

When

With meals (improves iron absorption, reduces GI upset)

Condition-Based Dosing

General antioxidant and immune support

200 - 500 mg/day— Tissue saturation at ~200 mg/day; diminishing returns above 400 mg

During common cold (therapeutic)

1,000 - 2,000 mg/day split into 2-3 doses— Start at symptom onset; 15% severity reduction in meta-analysis

Intense physical training / athletes

500 - 1,000 mg/day during heavy training periods— 50% reduction in cold incidence under extreme physical stress

Smokers

Additional 35 mg/day above RDA (minimum); 200-500 mg/day ideal— Smokers have higher oxidative stress and lower vitamin C levels

Collagen support and skin health

250 - 500 mg/day— Essential cofactor for proline and lysine hydroxylation in collagen

Iron absorption enhancement

100 - 200 mg taken with iron-rich meal or iron supplement— Can increase non-heme iron absorption 2-3 fold

Safety & Limits

Upper Safe Limit

2,000 mg/day (UL for adults; GI distress above this)

Cycling

Safe for continuous use

Contraindications

History of kidney stones (oxalate; high doses may increase risk)

Hemochromatosis or iron overload (enhances iron absorption)

G6PD deficiency (high IV doses can cause hemolytic anemia)

End-stage renal disease (impaired oxalate clearance)

Concurrent chemotherapy (discuss with oncologist before supplementing)

Synergies

Iron

Vitamin C dramatically enhances non-heme iron absorption

Collagen

Essential cofactor for collagen synthesis; mandatory for collagen efficacy

Vitamin E

Vitamin C regenerates oxidized vitamin E, extending antioxidant protection

Zinc

Complementary immune support via different mechanisms

Avoid Combining With

✕High-dose vitamin C may interfere with certain lab tests (false glucose readings)
✕Copper (very high vitamin C may reduce copper absorption)
✕Chemotherapy drugs (antioxidant may theoretically reduce efficacy — consult oncologist)

Updated 4/15/2026