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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.

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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.

How to take it

TimingSplit into two doses if you take more than a token amount - plasma anthocyanins peak within 1-2 hours and clear quickly.
With food?With food, which is how anthocyanins are consumed in the diet and how they were dosed in the trials.
Worth knowingA punnet of blackcurrants, blackberries or aronia delivers the same anthocyanins for less money than an isolated C3G capsule with no trial behind its dose.

Interactions

With medications

  • warfarin, direct oral anticoagulants, aspirin and other antiplatelets

    Berry anthocyanins have mild antiplatelet activity that adds to bleeding risk. tell your prescriber before starting and stop two weeks before surgery

With other supplements

  • fish oil, ginkgo, garlic and high-dose vitamin E

    Additive antiplatelet effect across several mild agents. be aware of the total if you stack several, especially before a procedure

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does C3G improve night vision?

No. A systematic review of placebo-controlled trials of bilberry anthocyanins found the more rigorous studies were negative for night vision, and studies of dark adaptation found no meaningful effect, so the evidence for cyanidin-3-glucoside (C3G) is limited.

Did RAF pilots really eat bilberries for night vision?

The night-vision claim for C3G and berry anthocyanins stems from a Second World War legend about RAF pilots, and placebo-controlled trials have mostly failed to find a night-vision effect.

How much cyanidin-3-glucoside should I take?

Berry anthocyanin trials used roughly 50-300 mg of total anthocyanins daily; isolated C3G supplements list 50-150 mg without trial support. Blackcurrants, blackberries or aronia provide the same anthocyanins as food.

Is C3G safe with blood thinners?

Berry anthocyanins such as C3G have mild antiplatelet activity, so tell your prescriber if you take warfarin, a direct oral anticoagulant or aspirin, and stop two weeks before surgery.

Scientific references

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