Holds collagen together, recycles other antioxidants, and powers your stress response.
Mechanisms, studies and evidence grades for each claim above.
RDA ~75 mg/day (women), 90 mg/day (men); smokers +35 mg/day. Upper limit 2,000 mg/day.3 Humans lost the capacity to synthesize vitamin C and must obtain it entirely from diet.3
↑ back to summaryAbsorbed via sodium-dependent transporters — SVCT1 in the gut, SVCT2 in peripheral tissue and brain. Transport is coupled to sodium gradients, which is the mechanistic link back to electrolyte status.7
↑ back to summaryMaintains iron in its reduced form (Fe²⁺), which enables prolyl and lysyl hydroxylase activity — the step that stabilizes the collagen triple helix. Deficiency produces impaired collagen stability, which is the mechanism behind scurvy.1 (Strong — human evidence) The same mechanism underlies wound healing: systematic review of clinical trials finds supplementation improves healing outcomes in several tissue-injury contexts, though study quality is mixed.16 (Moderate — mixed trial quality)
↑ back to summaryOxidative stress. Acts as a reducing agent that neutralizes reactive oxygen species; protects lipids, proteins, and DNA from oxidative damage; regenerates other antioxidants including vitamin E.2 (Strong)
Brain. Concentrated in neurons; supports antioxidant defense2 and neurotransmitter synthesis, including norepinephrine;5 transported in via SVCT2.7
Immune. Supports leukocyte function and reduces oxidative stress during infection.6
Heart. Maintains tetrahydrobiopterin (BH4), a cofactor for nitric oxide synthase — supports vascular nitric oxide production and, per the glycine/collagen entry, may help reduce atherosclerotic plaque via this route.89 (Moderate)
Gut. Enhances non-heme iron absorption by reducing Fe³⁺ to Fe²⁺;4 absorbed itself via SVCT1 in the intestinal epithelium.7
Adrenal / stress response. The adrenal cortex and medulla hold some of the highest vitamin C concentrations of any tissue; ACTH stimulation triggers measurable vitamin C secretion from the gland into circulation as part of the stress response, and ascorbate is a cofactor for dopamine β-hydroxylase, the enzyme that produces the stress hormone norepinephrine.115 (Moderate — human evidence)
Reproductive health. Concentrated in the corpus luteum; supplementation raised serum progesterone and pregnancy rate in women with a luteal phase defect.12 In men, it makes up the majority of seminal fluid's antioxidant capacity, and small trials found supplementation improved sperm count, motility, and morphology.13 (Moderate — small human trials)
Bone. Higher dietary intake correlates with greater bone mineral density in observational cohorts, consistent with its cofactor role in synthesizing the type I collagen that forms bone's organic matrix.14 (Moderate — observational)
Histamine metabolism. Experimental depletion-repletion studies show blood histamine rises as vitamin C status falls, consistent with a cofactor role in histamine breakdown via diamine oxidase.10 (Moderate — human depletion/repletion study)
Cellular energy. Ascorbate is classically described as a cofactor for the two hydroxylases in carnitine biosynthesis — the pathway that shuttles fatty acids into mitochondria for beta-oxidation — and human depletion studies show plasma carnitine falls alongside vitamin C.10 However, a knockout-mouse study found vitamin C is not strictly essential for carnitine synthesis in vivo.15 (Weak — contested)
Detoxification. As a reducing agent, vitamin C plausibly helps quench reactive intermediates generated during phase I cytochrome P450 liver metabolism, but this is inferred from its general antioxidant mechanism2 rather than demonstrated in direct outcome trials on detox pathways. (Weak — mechanistic only)
↑ back to summaryScurvy: impaired collagen synthesis presenting as bleeding gums, poor wound healing, and fatigue.1
↑ back to summaryVitamin C is a documented, high-confidence cofactor for prolyl and lysyl hydroxylase in collagen biosynthesis.1 (Strong — human evidence) See the Glycine / Collagen entry for the full synthesis chain this feeds into.
↑ back to summary| Food | Vitamin C (approx.) |
|---|---|
| Black currants | ~200 mg / cup (~222% DV) |
| Red bell pepper | ~190 mg / cup raw (~211% DV) |
| Kiwi | ~130–170 mg / 2 fruit (~145–189% DV) |
| Brussels sprouts | ~95 mg / cup cooked (~106% DV) |
| Broccoli | ~80–100 mg / cup cooked (~89–111% DV) |
| Strawberries | ~85 mg / cup (~94% DV) |
| Orange | ~70–80 mg / medium fruit (~78–89% DV) |
| Orange juice | ~60–90 mg / 8 oz (~67–100% DV) |
| Tomato | ~17 mg / medium fruit (~19% DV) |
| Potato (baked) | ~20 mg / medium (~22% DV) |