Vitamin C
Water-soluble vitamin that contributes to the normal function of the immune system and to the protection of cells from oxidative stress.
Also known as Ascorbic Acid, Vit C
Common doses
500-2000 mg
Best timing
Morning
Food
With or without food
Interactions
6 known
Vitamin C (ascorbic acid) is a water-soluble vitamin and one of the most well-known antioxidants. Humans cannot synthesise it and must obtain it from diet or supplements. It is essential for collagen synthesis, immune function, iron absorption, and antioxidant defence.
Despite being one of the most studied vitamins, Vitamin C remains surrounded by controversy. Linus Pauling's advocacy for mega-dose Vitamin C in the 1970s launched decades of research, but the evidence for high-dose supplementation (>1,000 mg) preventing colds or treating cancer remains weak. At standard supplement doses (200-500 mg), Vitamin C is well-supported for immune function and collagen synthesis.
Vitamin C is water-soluble, meaning excess is excreted in urine. This makes toxicity rare but also means the body cannot store large amounts. Splitting doses throughout the day maintains more consistent blood levels than a single large dose.
Key benefits
Immune function
Vitamin C contributes to the normal function of the immune system. Regular supplementation may reduce cold duration by 8-14% in adults.
Collagen synthesis
Vitamin C contributes to normal collagen formation for the normal function of skin, bones, teeth, and cartilage.
Iron absorption
Vitamin C increases the absorption of non-heme iron by converting it from the ferric to the more absorbable ferrous form.
Antioxidant protection
Vitamin C contributes to the protection of cells from oxidative stress. It regenerates other antioxidants including Vitamin E and glutathione.
Available forms
Ascorbic Acid
The standard form. Cheapest and most studied. Can cause stomach upset at high doses. Best taken with food.
Sodium Ascorbate
Buffered (non-acidic). Gentler on the stomach. Contains sodium, so consider if on a sodium-restricted diet.
Liposomal Vitamin C
Encapsulated in phospholipid spheres. May provide higher bioavailability than standard ascorbic acid. More expensive.
Ester-C (Calcium Ascorbate)
Buffered form. Contains calcium. Marketed as longer-lasting, though evidence for superiority is limited.
Food sources
- Bell peppers (red and yellow)
- Citrus fruits (oranges, lemons)
- Strawberries and kiwi
- Broccoli and Brussels sprouts
- Tomatoes
- Guava (highest per serving)
Signs of deficiency
- Easy bruising
- Slow wound healing
- Dry, splitting hair
- Bleeding gums
- Rough, dry skin
- Frequent infections
- Fatigue
Upper intake limit
2,000 mg/day (NIH). Higher doses may cause diarrhoea and GI distress. The body's absorption efficiency drops significantly above 200 mg per dose.
Research summary
Strong evidence for collagen synthesis, iron absorption enhancement, and antioxidant function. Moderate evidence for reducing cold duration (not prevention). Weak evidence for mega-dose therapy in cancer or other diseases. The most practical approach: 200-500 mg daily from supplements, plus dietary sources.
Known interactions (6)
High-dose Vitamin C may degrade B12
Vitamin C can neutralise selenite in the gut
Vitamin C boosts iron absorption
Complementary antioxidant recycling
Vitamin C is essential for collagen synthesis
Vitamin C recycles oxidised quercetin
Check your full stack
for interactions.
See what competes, what combines well, and when to take everything. Every interaction cites a published source.
Stack
6 supplements
Stack review
1 flagZinc and Iron compete for the same absorption pathway. Take at least 2 hours apart.
Supplements
This information is for educational purposes only. It is not medical advice and does not diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional.