Ascorbic acid · L-ascorbic acid
500 mg · vegan · gluten-free · 100 caps
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An essential water-soluble vitamin that humans cannot synthesize. Required for collagen synthesis, antioxidant defense, carnitine production, and immune cell function. Found in citrus, peppers, and cruciferous vegetables — but modern diets and storage often fall short of optimal intake.
Acts as a cofactor for hydroxylase enzymes in collagen synthesis, as a water-soluble antioxidant scavenging free radicals, and as an electron donor regenerating vitamin E. In immune cells, it accumulates at high concentrations and supports neutrophil chemotaxis and phagocytosis. The cold-shortening effect is thought to involve both antioxidant and direct antiviral mechanisms.
People with low dietary intake of fruits and vegetables · smokers (vitamin C requirements are higher) · those under physical stress or in cold environments · anyone wanting a low-cost immune adjunct · people concerned about collagen and vascular health.
Hemochromatosis (vitamin C increases iron absorption), history of kidney stones (theoretical concern at high doses, though evidence is mixed), G6PD deficiency (rare hemolytic risk at very high doses), iron overload conditions.
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✓ Split BID for better absorption
✓ Split BID for better absorption
✓ Reduces stomach upset at higher doses
Vitamin C is a water-soluble electron donor that regenerates vitamin E, supports collagen hydroxylation, and accumulates in immune cells to support neutrophil function. The cold-shortening effect likely involves both antioxidant protection of immune cells and direct antiviral activity.
From Hemilä Cochrane reviews. Effects are modest but consistent.
Modeled trajectory based on cited keystone trials
Plasma µmol/L. Saturation occurs around 70–80 µmol/L; doses above 400 mg/day provide diminishing returns.
29 trials · n=11,350 · Cochrane review
→ No prevention in general population; 8% duration reduction in adults, 13.6% in children; 50% incidence reduction in athletes under severe physical stress
15 comparisons · 10 trials · severe vs mild symptoms
→ Vitamin C decreased severity of common cold by 15%; greater effect on severe symptoms than mild; no effect on mild symptom duration
Narrative review · mechanism focus
→ Vitamin C supports epithelial barriers, neutrophil chemotaxis and phagocytosis, and lymphocyte proliferation; deficiency impairs immunity
B · B for cold duration reduction in regular supplementation (strong Cochrane evidence, consistent effect). B− for cold prevention in general population (no effect). A− for immune support in deficiency (well-established physiology). C+ for therapeutic use after symptom onset (weaker evidence than prophylactic). Safety is excellent at typical doses; GI upset at >2 g/day; theoretical kidney stone risk at very high chronic doses.
A plain-English read of the literature behind this supplement. Not a clinical recommendation.
Vitamin C is the most famous supplement in history, largely due to Linus Pauling's 1970 book "Vitamin C and the Common Cold," which claimed megadoses could prevent and cure colds, cancer, and heart disease. The cancer and cardiovascular claims have been refuted by large trials. The cold claims were partially correct — there is a real but modest effect — but the megadose framing is not supported by modern evidence.
The Hemilä 2013 Cochrane review is the definitive assessment: 29 trials with 11,350 participants. Routine supplementation did not reduce cold incidence in the general population (RR 0.96). But in a subgroup of 642 marathon runners, skiers, and soldiers in sub-arctic exercises, the pooled RR was 0.50 — a 50% reduction. The benefit is specific to brief periods of severe physical stress.
For duration, regular supplementation shortened colds by 8% in adults and 13.6% in children. Therapeutic use started after symptoms began showed no significant benefit in the Cochrane analysis — though the 2023 Hemilä meta-analysis found that vitamin C decreased severe symptom severity by 15%, with no effect on mild symptoms. This suggests that if vitamin C helps therapeutically, it helps with the miserable part of a cold, not the sniffles.
The absorption kinetics explain why megadoses are inefficient. Intestinal absorption is saturable via sodium-dependent vitamin C transporters (SVCT1). At 30–200 mg doses, 70–90% is absorbed. At 1000 mg, absorption drops to ~50%. At 12 g, ~16%. Unabsorbed ascorbic acid draws water into the bowel, causing osmotic diarrhea — the body's natural brake on excessive intake.
Practical guidance: 200–500 mg split BID for daily supplementation (better absorption than 1000 mg once daily). If you're an athlete or facing severe physical stress, 500–1000 mg/day prophylactically. At cold onset, some evidence supports 6–8 g/day in divided doses started within 24 hours — but the therapeutic evidence is weaker than the prophylactic evidence.
Keystone references: Hemilä & Chalker 2013 (Cochrane Database Syst Rev, PMID 17636648 — definitive Cochrane review); Hemilä & Chalker 2023 (BMC Public Health, PMID 38082300 — severity meta-analysis); Carr & Maggini 2017 (Nutrients, PMID 29099763 — immune mechanism review).
How to use Vitamin C specifically for Fatigue — the right dose, timing, blood markers to track, and how to know if it is working.
A clinical evidence review of Vitamin C — RCT data, effect sizes, evidence grade, and what the numbers mean for your specific situation.
Everything you need to know about Vitamin C — mechanism, dose, safety, buying guide for India, and what the research actually says.
Essential for immune function, testosterone maintenance, and wound healing — but the form and dose matter enormously, and long-term high-dose use causes copper deficiency.
BUY →Flavonoid antihistamine that stabilizes mast cells and blocks histamine release at the source.
BUY →The single supplement with the strongest evidence base for a healthy human — if you actually take enough.
BUY →SacredBod's longer take on Vitamin C — context the structured blocks above don't capture.
Vitamin C is the most famous supplement in history, largely because of Linus Pauling’s 1970 book claiming megadoses could prevent and cure colds, cancer, and heart disease. The cancer and cardiovascular claims have been refuted. The cold claims were partially correct — there is a real but modest effect — but the megadose framing is not supported by modern evidence.
The Hemilä 2013 Cochrane review is definitive: 29 trials, 11,350 participants. Routine supplementation did not prevent colds in ordinary people. But in 642 marathon runners, skiers, and soldiers in sub-arctic exercises, the incidence dropped 50%. The benefit is specific to brief periods of severe physical stress.
For duration, regular supplementation shortens colds by 8% in adults and 13.6% in children. The 2023 Hemilä meta-analysis found vitamin C decreased severe symptom severity by 15% — it may help with the miserable part of a cold, not the sniffles.
Absorption kinetics explain why megadoses waste money. Intestinal absorption is saturable: 70–90% at 200 mg, ~50% at 1000 mg, ~16% at 12 g. Unabsorbed ascorbic acid causes osmotic diarrhea — the body’s natural brake.
Practical guidance: 200–500 mg split BID for daily use. If you’re an athlete or facing severe stress, 500–1000 mg/day prophylactically. At cold onset, 6–8 g/day in divided doses within 24 hours may help, but therapeutic evidence is weaker than prophylactic.
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