Limited evidenceEye health

Cyanidin-3-Glucoside (C3G)

The main anthocyanin in blackcurrant, bilberry and dark berries, sold for night vision on the strength of a Second World War legend about RAF pilots. Placebo-controlled trials of berry anthocyanins have mostly failed to find a night-vision effect.

Evidence last reviewed: August 2026

What the science says

Improving night vision Limited evidence
A systematic review of placebo-controlled trials of bilberry anthocyanosides for night vision found that the more rigorous studies were negative, and concluded the hypothesis was not supported. The positive reports came from earlier, weaker designs.
Dark adaptation and recovery after glare Limited evidence
Placebo-controlled crossover studies of blueberry anthocyanins measuring dark vision and recovery after photobleaching found no meaningful effect on these outcomes. This directly tests the mechanism most often claimed for C3G.
Antioxidant effects in the retina Limited evidence
Cell and animal work shows that cyanidin-3-glucoside is a potent antioxidant with activity in retinal tissue models. Human bioavailability of anthocyanins is low and short-lived, and no clinical outcome has been demonstrated from this mechanism.

Dosage & safety

Studied doseTrials of berry anthocyanins used roughly 50–300 mg of total anthocyanins daily; isolated C3G supplements commonly list 50–150 mg as a label dose without trial support. Absorption is poor, with plasma levels peaking within 1–2 hours and clearing quickly.

SafetyAnthocyanins from berries have a strong food safety record and adverse effects in trials were minimal. Concentrated extracts are less well characterised. Berry anthocyanins have mild antiplatelet activity, so use caution with anticoagulants and before surgery. Limited data in pregnancy and breastfeeding.

Scientific references

Anthocyanosides of Vaccinium myrtillus (bilberry) for night vision--a systematic review of placebo-controlled trials
Canter PH, Ernst E — Surv Ophthalmol, 2004
Blueberry effects on dark vision and recovery after photobleaching: placebo-controlled crossover studies
Kalt W, McDonald JE, Fillmore SA — J Agric Food Chem, 2014

Where to buy

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