What do the trials actually say — after the megadose myth's four decades?
Vitamin C's evidence base is one of the largest in nutrition science — 60+ cold trials alone, the gout urate metas, the cardiovascular-marker literature, and the cancer-megadose nulls — and its honest summary is the clearest demonstration of this library's population-conditional principle: the benefits concentrate in the deficient, the stressed (extreme exercise), and the specific doses the trials used, with the megadose claims (prevention, cure, 'immune boosting') retired by the very trials the Pauling era launched. This chapter reads the cold verdict, the urate meta, and the honest boundaries.
The field that retired the megadose myth teaches calibrated reading at its cleanest:
The first controlled clinical trial in medical history: citrus cures scurvy, the other five treatments don't. The evidence that took the Admiralty 48 years to adopt.
Lemon juice becomes standard naval issue; scurvy vanishes from the Royal Navy. The disease that killed more sailors than battles, ended.
The antiscorbutic factor finally a molecule (from paprika, of all sources) — the 1937 Nobel follows, and the structure is solved.
The double Nobel laureate argues grams of vitamin C prevent colds and transform health — the most credentialed advocate a supplement ever had.
60+ trials answer Pauling's prediction: no prevention in the general population, modest duration benefit — the megadose myth retired by its own era's research.
The modest duration finding, the extreme-exercise subgroup, the urate meta (our gout page), and the liposomal-delivery frontier — the vitamin's honest size after the myth.
POPULATION · Cancer patients across high-dose IV vitamin C trials
FINDING · The IV-megadose oncology trials have been consistently disappointing — no demonstrated survival or tumor-response benefit in the Phase-III-quality studies.
LIMITATION · The null is the finding; the pharmacologic IV doses achieve plasma levels unattainable orally, but the outcome trials have not followed. The IV protocol remains experimental, and the IV-bar consumer version is the null's wellness repackaging.
POPULATION · Adults across observational and interventional studies
FINDING · Higher dietary vitamin C intake associates with lower cardiovascular risk in cohorts; the supplementation trials in replete populations show null or modest marker effects.
LIMITATION · The cohort association is confounded (vitamin-C-rich diets are plant-rich diets); the intervention nulls in the replete population are the honest boundary. The food, not the pill, carries the signal.
POPULATION · Men across large cohort studies (Health Professionals Follow-up Study)
FINDING · Men consuming 1,000+ mg supplemental vitamin C daily had a ~19% higher risk of kidney stones — the dose-dependent oxalate mechanism our kidney-stones page teaches.
LIMITATION · Observational (supplement users differ); the mechanism (oxalate metabolism) is direct and biologically grounded. The stone caution at high chronic doses is one of the category's real harms — the reason the megadose habit carries a cost.