Vitamin C
Also known as Ascorbic acid
Vitamin C is a water-soluble antioxidant essential for collagen synthesis, immune function, and the regeneration of other antioxidants. It also dramatically improves absorption of plant-based (non-heme) iron.
Benefits
Boosts iron absorption
StrongConverts non-heme iron to a form the gut absorbs far more readily.
Supports collagen and skin
StrongA required cofactor for collagen synthesis and skin repair.
Immune support
ModerateMay modestly reduce the duration of colds with regular intake.
Pros & cons
Pros
- Cheap and very safe
- Strong synergy with iron
- Water-soluble, low toxicity
Cons
- Excess is excreted, not stored
- Megadoses offer little extra benefit
Side effects
GI upset at high doses
Doses above ~1,000 mg can cause loose stools.
How to take it
Typical dose
200–1,000 mg per day
Timing
With iron-rich meals to maximize iron uptake
Common forms
What the research says
[1]Vitamin C and iron absorption
StrongCo-ingestion markedly increases non-heme iron absorption in controlled studies.
Nutrition trials · 2014PubMed[2]Vitamin C and the common cold
ModerateRegular supplementation modestly shortens cold duration but does not reliably prevent colds.
Cochrane review · 2013PubMed
How Vitamin C interacts
Synergies, absorption effects, and cautions between Vitamin C and other supplements in the matrix.
Vitamin C and its direct connections · click a node to open its guide
Taken together, vitamin C can multiply the absorption of plant-based iron.
Compare the pairingVitamin C is a required cofactor for the enzymes that build collagen, so adequate vitamin C supports both dietary collagen and the body's own production.
Compare the pairingVitamin C regenerates oxidised glutathione back to its active form, amplifying NAC's antioxidant effect.
Compare the pairingVitamin C protects nitric oxide from oxidative breakdown, extending the vasodilatory effect of arginine.
Compare the pairingVitamin C protects nitric oxide from oxidative degradation, extending the vasodilatory effect of citrulline-derived NO.
Compare the pairingBoth are heavily used in adrenal cortex and steroid hormone synthesis.
Compare the pairingVitamin C is required for collagen synthesis, which underpins skin, hair, and nail structure alongside biotin.
Compare the pairingVitamin C supports cartilage matrix and collagen formation alongside glucosamine's role in joint tissue.
Compare the pairingHigh-dose niacin may modestly raise blood sugar; vitamin C does not eliminate this risk, especially in diabetics.
Compare the pairingFrequently asked questions
What is Vitamin C used for?
Vitamin C is most commonly used for immunity, skin health, and antioxidant. Converts non-heme iron to a form the gut absorbs far more readily.
How much Vitamin C should I take?
A typical dose is 200–1,000 mg per day. Start at the lower end and confirm the right dose for you with a healthcare professional.
When is the best time to take Vitamin C?
Recommended timing: With iron-rich meals to maximize iron uptake.
What are the side effects of Vitamin C?
Reported side effects include gi upset at high doses. Doses above ~1,000 mg can cause loose stools.
More Vitamins
Folate (B9)
The active B vitamin behind methylation, mood, and pregnancy health.
Vitamin B1 (Thiamine)
The energy metabolism cofactor that keeps nerves and muscles firing.
Vitamin B12 (Cobalamin)
The methylation and nerve-health vitamin that protects the brain and blood.
Compare Vitamin C with
Weighing your options? See how Vitamin C stacks up against similar supplements.