Evidence brief · Supplement
Vitamin C for Cancer / CVD prevention
Evidence grade D — Oral megadose trials null
- Overall grade
- Grade D
- Last revised
- 1
- graded outcome
- 1
- reference listed
Assembled by the app from other entries in this library. It adds no evidence of its own — follow the links to the entries it draws on.
1 at grade D — 1 graded row
What is known
Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.
- Cancer / CVD preventionEvidence grade D
Oral megadose trials null
Trivialhigh
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Thin evidence: Cancer / CVD prevention (grade D).
The evidence in words
The verdict
For cancer / cvd prevention, Vitamin C earns evidence grade D (trivial effect, high consistency) — the evidence does not support the claim. Oral megadose trials null
How it might work
Ascorbate donates electrons, regenerating other antioxidants and serving as a cofactor for prolyl and lysyl hydroxylases that stabilize collagen's triple helix — which is why deficiency causes the connective-tissue breakdown of scurvy. In the gut it reduces ferric to ferrous iron, sharply improving non-heme (plant) iron absorption.
How to use it
75–120 mg/day covers requirements; 200–500 mg is a common well-absorbed supplemental dose. Split doses above ~500 mg — absorption fraction falls as the dose rises. Take with a plant-iron source when the goal is iron absorption.
Safety & cautions
Very safe; excess is excreted. Very high doses can cause GI upset and, in susceptible people, raise oxalate and kidney-stone risk. High-dose vitamin C can distort some point-of-care glucose meters and, at gram doses, may affect warfarin control.
Bottom line
Eat the fruit and vegetables; a 200–500 mg supplement is a reasonable, cheap margin. Best evidence-backed uses are preventing deficiency, supporting collagen, shortening colds slightly, and boosting plant-iron uptake — not curing disease.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Requirement
- 75–120 mg/day from food or supplement.
- Supplemental
- 200–500 mg/day; split larger doses.
Goes with
- Vitamin CRead the full Vitamin C monographEvidence grade A
Related reading
Entries that share this one's tags or conditions.
- Vitamin C for Cold durationEvidence grade B — Cochrane: modest shortening, not preventionEvidence grade B
- Vitamin C for Non-heme iron absorptionEvidence grade A — ~2–3× when taken togetherEvidence grade A
- Vitamin C for Scurvy / deficiencyEvidence grade A — DefinitionalEvidence grade A
- Vitamin C: dosage and how to take it75–120 mg/day from food or supplement.Evidence grade A
Sources
As this entry records them: title, journal and year. None carries a DOI or PubMed id, so none is linked as a verified paper. Each link searches PubMed for the title; check that what you find is what the entry describes.
- 1.Vitamin C for preventing and treating the common cold (Cochrane review) — Cochrane Database Syst Rev, 2013. Search PubMed (opens in a new tab)
Last revised . A grade is this entry's reading of the evidence, not medical advice.