Supplement analysis backed by scientific evidence · PT

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Limited evidenceVitamins & minerals

Citrus Bioflavonoid Complex

Flavonoids from citrus peel, sold since the 1930s as a vitamin C companion for capillaries. That original claim was never substantiated; the modern evidence is a surrogate-marker improvement in blood-vessel function.

Evidence last reviewed: August 2026

What the science says

  • Endothelial function Moderate evidence

    A dose-response meta-analysis of 8 randomized trials (596 participants) found citrus flavonoid supplements improved flow-mediated dilation by 2.75 percentage points, rising with dose. Heterogeneity was very high (I²=87%) and FMD is a surrogate marker, not a clinical outcome.

  • No cognitive benefit Moderate evidence

    A 36-week randomized placebo-controlled trial in 80 older adults with subjective cognitive decline found citrus peel extract no better than placebo on the primary cognitive endpoint or on inflammation (IL-8); both groups improved equally.

  • The capillary and vitamin C claims are unsupported Limited evidence

    The traditional selling point — that bioflavonoids strengthen capillaries or potentiate vitamin C, the old "vitamin P" idea — has no supporting modern randomized trial, and bioflavonoids are not a vitamin.

Dosage & safety

Studied doseProducts typically supply 500–1000 mg of mixed citrus bioflavonoids daily. Trials used a wide range of preparations (hesperidin, naringenin, citrus peel extracts) at doses roughly 200–800 mg/day, so no standard dose exists.
SafetyWell tolerated; mild digestive upset is the usual complaint. Citrus flavonoids and grapefruit-derived preparations can inhibit CYP3A4 and raise levels of statins, calcium channel blockers and some immunosuppressants — a real interaction risk with concentrated extracts. Limited data in pregnancy.

Scientific references

Where to buy

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