Vitamin C

Supplements · Vitamins · Supplement, Typed Supps

Useful, but it will not stop you catching a cold.

Stage by stage

Intake (Tablet or powder): Water-soluble, so it dissolves and moves quickly without needing fat or bile.
Digestion & absorption (SVCT1 transporter): Dissolves rapidly in stomach fluid, then a dedicated transporter (SVCT1) pulls it into the small intestine — though this saturates above roughly 1g at once.
Bloodstream (Freely circulating): Travels unbound, with levels rising within a couple hours of a dose.
Collagen-building cells (Enzyme cofactor): Required cofactor for building collagen, the structural protein in skin and connective tissue.

What the evidence supports

Preventing scurvy — strong evidence. Settled since the 18th century. A small daily amount prevents it completely.
Shortening a cold once you already have one — moderate evidence. Pooled trials show roughly an 8% shorter cold in adults — under a day. Real, but smaller than the reputation.
Preventing colds in the general population — insufficient evidence. Regular supplementation does not reduce how often ordinary adults catch colds. This is one of the best-tested negative findings in the field.
Preventing colds in people under extreme physical stress — moderate evidence. In marathon runners, skiers, and soldiers in sub-arctic conditions, incidence was roughly halved — a genuine exception rather than a loophole.
Improving iron absorption from plant foods — strong evidence. A well-characterised chemical effect: it converts non-heme iron into the form the gut transporter accepts.

Typical dose

250–500 mg daily, split into two doses

Upper limit: 2,000 mg daily for adults

Timing

Splitting one dose into two across the day improves total absorption.

Time to effect

Hours: Blood levels rise quickly.
Ongoing: Maintains collagen and antioxidant support.

Medication interactions

Warfarin: Very high doses have been reported to interfere with anticoagulant control. Ordinary doses appear fine, but tell whoever manages your INR. (moderate)
Chemotherapy and radiotherapy: High-dose antioxidants during treatment are controversial and could theoretically interfere. Ask your oncology team rather than deciding alone. (high)

Common myth

“Vitamin C prevents colds.” In reality: Regular supplementation doesn’t reduce how often you catch a cold for most people — only a modest shortening of duration.

Food sources

Apple Juice — Drink
Bell Peppers — Vegetable
Bitter Melon — Vegetable
Blackcurrant — Fruit
Blood Orange — Fruit
Breadfruit — Fruit