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Longevity Atlas
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Vitamin C

Doesn't prevent colds but shortens them 8% when taken regularly; aids iron absorption and collagen synthesis. Easily covered by food.

3/5Estimated monthly cost: ≈ 3
Dose

200–500 mg daily if fruit and vegetables are scarce; above 1 g diarrhoea and kidney-stone risk in men.

Timing

Together with iron; in split doses.

Cautions

Under 500 mg with kidney-stone history; avoid in haemochromatosis (boosts iron uptake).

What it is

A water-soluble antioxidant and enzyme cofactor; absorption saturates above 200 mg.

What the evidence shows

Cochrane (29 RCTs, n=11,306): regular use –8% cold duration in adults, –14% in children; starting at onset does nothing. Halved colds in marathoners and soldiers.

Goals

ImmunitySkin, hair

Last reviewed: 6 September 2026

This site is educational and does not replace medical advice. Start any supplement or drug only after consulting a doctor or pharmacist.