Vitamin C

Your intake

What each level of vitamin c does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

1. Severely lowYOU ARE HERE

   0 mg – 29.7 mg

   Well below target. Risk of deficiency symptoms tied to antioxidant · collagen.

2. Insufficient

   29.7 mg – 90 mg

   Below the recommended daily target. Long-term adequacy not assured.

3. Adequate

   90 mg – 135 mg

   Daily target met. Standard nutritional support for antioxidant · collagen.

4. Therapeutic

   135 mg – 180 mg

   Common for specific health goals. Check the evidence for your situation before sustaining this level.

5. High

   180 mg – 2000 mg

   Approaching the tolerable upper limit. Monitor and consider clinical guidance.

6. Over upper limit

   2000 mg – +

   Above the tolerable upper limit. Risk of adverse effects — back off or consult a clinician.

Overview

Ascorbic acid is a water-soluble antioxidant and cofactor for hydroxylation reactions including collagen synthesis, carnitine synthesis, and the conversion of dopamine to norepinephrine. Humans lost the gulonolactone oxidase gene that lets most mammals synthesise it — we're stuck with dietary intake.

Functions

• ●Cofactor for prolyl and lysyl hydroxylases in collagen synthesis
• ●Reduces non-heme iron from ferric (Fe3+) to absorbable ferrous (Fe2+) in the gut
• ●Recycles oxidised vitamin E back to active form
• ●Cofactor in carnitine, catecholamine, and bile acid synthesis
• ●Regenerates tetrahydrobiopterin (BH4) for serotonin/NO synthesis

Mechanism

Donates two electrons to oxidised substrates, becoming dehydroascorbate; recycled by glutathione and NADH. The collagen role explains scurvy: without ascorbate, prolyl and lysyl hydroxylation fails, the collagen triple helix is unstable, and connective tissue breaks down (bleeding gums, joint pain, poor wound healing).

Benefits

• ●Treats and prevents scurvy
• ●Modestly shortens cold duration (~10–15%) when taken at onset
• ●Improves non-heme iron absorption ~3–4× when co-ingested
• ●High-dose IV vitamin C has experimental role in oncology and sepsis (mixed RCTs)

Deficiency

Severe scurvy is rare in the developed world but subclinical insufficiency is more common than appreciated — particularly in smokers, men with poor diets, and institutionalised elderly.

Excess

Generally well-tolerated; doses above ~2 g/day cause osmotic diarrhea. Long-term high-dose use modestly increases oxalate kidney stone risk in predisposed individuals.

Forms

• Ascorbic acid
  Standard, inexpensive, well-absorbed; mildly acidic
• Sodium / calcium ascorbate
  Buffered mineral salts; gentler on stomach
• Liposomal vitamin C
  Phospholipid encapsulation; ~2× plasma AUC vs equal-dose ascorbic acid
• Ascorbyl palmitate
  Fat-soluble derivative; antioxidant in cosmetics; oral relevance limited

Food sources

• Red bell pepper (raw) · 1 medium150 mg
• Orange · 1 medium70 mg
• Kiwifruit · 1 medium65 mg
• Strawberries · 1 cup85 mg
• Cooked broccoli · 1 cup100 mg
• Brussels sprouts (cooked) · 1 cup95 mg

Supplement forms

Plain ascorbic acid is fine and inexpensive. 'Buffered' mineral ascorbates (sodium, calcium, magnesium ascorbate) are gentler on the stomach. Liposomal forms achieve modestly higher plasma peaks but at meaningful cost premium. Doses above 500 mg in a single sitting are largely excreted unchanged.

Bioavailability

Absorbed in proximal small intestine via SVCT1 transporter (saturable). At 200 mg single dose, ~80% is absorbed; at 1 g, ~50%; at 5 g, only ~20%. Tissue saturation occurs around 400 mg/day from diet. Vitamin C from food = vitamin C from supplements at adequate doses.

Longevity relevance

Adequacy correlates with lower all-cause mortality across cohorts; supplementation in adequate adults shows no consistent benefit. The strongest signal is for whole-food fruit and vegetable intake — supplementation does not reproduce that effect.

Relationships

References

• NIH ODS — Vitamin Cguideline
• Linus Pauling Institute — Vitamin Creview
• Hemilä — vitamin C for the common cold (Cochrane 2013)review

About Vitamin C

Collagen synthesis, antioxidant, immune function.

Role

Antioxidant · collagen

Daily target

90 mg (DV)

Upper limit

2000 mg

Also called

vitamin c, ascorbic acid, l-ascorbic acid, sodium ascorbate, calcium ascorbate, magnesium ascorbate