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Buffered Vitamin C (Sodium Ascorbate)

Sodium ascorbate is biologically identical to ascorbic acid once absorbed. Its only genuine advantage is a neutral pH that is easier on the stomach at gram doses — and the tradeoff is a meaningful sodium load at those doses.

What the science says

  • Bioequivalent to ascorbic acid Strong evidence

    Absorption is limited by the SVCT1 transporter, not by the salt form. Classic pharmacokinetic work in healthy volunteers showed vitamin C absorption is essentially complete at 200 mg, falls to roughly 50% at 1250 mg, and drops to a small fraction at multi-gram doses — the same ceiling applies whether you take the acid or a buffered salt. Buffering changes gastric pH, not intestinal transport.

  • Gentler on the stomach at high doses Limited evidence

    This is the real reason clinicians use it in high-dose oral protocols, and the rationale is sound: ascorbic acid is acidic (pH ~2.5 in solution) and can irritate, while sodium ascorbate is near-neutral. But the more common complaint at multi-gram doses — osmotic diarrhoea from unabsorbed ascorbate reaching the colon — happens with buffered forms too, because it is a consequence of transporter saturation rather than acidity. Head-to-head tolerability trials are scarce.

  • Safer for the kidneys / reduces stone risk Limited evidence

    No. High-dose vitamin C in any form increases urinary oxalate excretion. A prospective cohort of 48,850 men found that vitamin C supplement users taking 1000 mg/day or more had roughly double the incidence of kidney stones (hazard ratio about 1.9) versus non-users. Buffering the acid does nothing to oxalate metabolism, and marketing that implies otherwise is misleading.

  • The sodium load is trivial Strong evidence

    Worth doing the arithmetic. Sodium ascorbate is about 11.6% sodium by weight, working out to roughly 110–130 mg of sodium per 1000 mg of vitamin C delivered. At 4 g/day of vitamin C that is around 500 mg of sodium — about a quarter of a strict 2000 mg/day restriction, from a supplement. At 250–500 mg/day it is negligible.

Dosage & safety

Studied doseFor repletion, 200–500 mg/day of any form is enough; the RDA is 75–90 mg/day. Buffered forms come into their own in high-dose protocols of 2–10 g/day taken in divided doses, where 'bowel tolerance' is the practical ceiling. Calcium ascorbate and magnesium ascorbate are alternatives if sodium is the limiting factor — each carries its own mineral load instead.
SafetyThe sodium content is the form-specific issue: relevant in hypertension, heart failure, chronic kidney disease and any medically supervised sodium restriction. GI effects — diarrhoea, cramping, bloating — are dose-dependent and set the practical limit for most people. Elevated urinary oxalate raises risk of calcium-oxalate stones and, in advanced CKD, oxalate nephropathy; anyone with reduced kidney function should not take gram doses. Enhanced non-haem iron absorption is a concern in haemochromatosis and transfusion-dependent thalassaemia. Very high doses can trigger haemolysis in G6PD deficiency. Vitamin C interferes with point-of-care glucose meters, faecal occult blood tests and some laboratory assays — mention it before testing. Not banned in sport.

Scientific references

Where to buy

California Gold Nutrition, Buffered Gold C®, GOLD Standard Sodium Ascorbate (Vitamin C), 240 Veggie Capsules

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