Vitamin C
Ascorbic acid · Foundation
Fully essential, rarely deficient in the developed world, and mostly oversold above dietary doses.
What the evidence says
Strong evidence for being essential; weak evidence for supplementation doing much in nourished adults. The honest cold finding: regular use modestly shortens duration (hours-to-a-day scale), while therapeutic use after symptom onset has not shown consistent benefit. High-dose injectable versions have no outcome evidence in healthy people.
What studies used
Physiological need is 75–120 mg/day; trials commonly used 200–1,000 mg, with the excess largely excreted. Published studies had not established a timing dependence.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- Doses above ~2 g commonly cause GI upset
- High-dose chronic use raises kidney-stone risk in predisposed men
Evidence base
established literature
Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.
This letter measures how much human research exists, not whether it works for you — the tier above (Strong) is the read on quality.
Research (12)
- Editorial: Vitamin C from bench to bedsideFront Nutr · 2024
- Vitamin CJ Am Med Assoc · 1950
- Vitamin C in dermatologyIndian Dermatol Online J · 2013
- Editorial: Vitamin C in Cancer and Infectious Diseases: Physiological, Biochemical and Therapeutic InterventionsFront Physiol · 2019
- Vitamin CPractitioner · 1959
- Vitamin CBr Med Bull · 1956
- Vitamin C and rheumatoid arthritisJ Chronic Dis · 1956
- Vitamin C for COVID-19 Treatment: Have We Got Enough Evidence?Front Nutr · 2022
- Vitamin C and exfoliative dermatitisBr J Dermatol · 1960
- [Pharmacological possibilities of vitamin C in oncology]Vnitr Lek · 2022
- [VITAMIN C]Dtsch Med Wochenschr · 1957
- Vitamin C Deficiency Can Present as True Hemolytic AnemiaIntern Med · 2026
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