Bilberry

Metadata

Approved Indications

Commission E (Germany)

• Approved (dried fruit): Acute, nonspecific diarrhea
• Approved (dried fruit): Mild inflammation of the mucous membranes of the mouth and throat (topical, as gargle or mouthwash)
• Note: Commission E monograph addresses only the dried fruit, not the anthocyanin-rich fresh fruit extract

ESCOP Monograph

• Approved: Peripheral vascular insufficiency and capillary fragility
• Approved: Venous insufficiency symptoms — heavy legs, pain, discomfort
• Approved: Improved microcirculation
• ESCOP addresses the anthocyanin-standardized extract from fresh fruit

EMA/HMPC

• Traditional use: Symptomatic relief of minor venous circulatory disturbances such as heavy legs (fresh fruit extract)
• Traditional use: Symptomatic treatment of nonspecific acute diarrhea (dried fruit)
• Traditional use: Symptomatic relief of minor inflammations of the oropharyngeal mucosa (dried fruit)
• EMA classified bilberry under traditional use only, noting insufficient clinical trial evidence for well-established use status

Agreement/Disagreement Between Bodies

• Broad agreement on dried fruit for diarrhea and oropharyngeal inflammation across Commission E and EMA
• ESCOP extends indications to peripheral vascular insufficiency and capillary fragility based on anthocyanin extract evidence
• EMA acknowledges vascular use but limits to “traditional use” classification
• Commission E does not address the anthocyanin-based vascular indications — its monograph predates much of the clinical research on standardized bilberry extracts
• All bodies agree on safety at recommended doses

Conditions Treated

Primary (Strong Evidence)

• Acute nonspecific diarrhea (dried fruit — tannin-mediated astringent effect)
• Peripheral vascular insufficiency and capillary fragility (anthocyanin extract)
• Mild oropharyngeal mucosal inflammation (dried fruit, topical)
• Minor venous circulatory disturbances — heavy legs, discomfort

Secondary (Moderate Evidence)

• Diabetic retinopathy — improved retinal microcirculation (several controlled trials with mixed results)
• Chronic venous insufficiency (overlap with horse chestnut and red vine leaf indications)
• Microcirculatory disorders (Raynaud-like phenomena, capillary permeability)

Traditional/Historical (Limited Evidence)

• Night vision improvement (popularized from WWII anecdotes about RAF pilots; not consistently supported by modern RCTs)
• Macular degeneration (preliminary, insufficient data)
• Urinary tract health (leaf preparations — folk medicine)
• Type 2 diabetes adjunct — blood glucose regulation (leaf and fruit — limited human data)
• Peptic ulcer (anthocyanins shown to be gastroprotective in animal models)

Mechanism of Action

Primary Mechanisms — Vascular Effects

Anthocyanin-mediated capillary stabilization

• Anthocyanins (particularly delphinidin and cyanidin glycosides) increase the synthesis of collagen and mucopolysaccharides in the vascular basement membrane
• Inhibit enzymes that degrade connective tissue: collagenase, elastase, and hyaluronidase
• Strengthen capillary walls, reducing permeability and fragility
• This is the principal mechanism underlying the ESCOP-approved vascular indications

Anti-edematous and venotonic effects

• Reduce capillary permeability by stabilizing endothelial cell junctions
• Decrease transcapillary filtration of plasma proteins and fluid
• Improve venous tone through effects on vascular smooth muscle

Antioxidant activity

• Anthocyanins are potent free radical scavengers (ORAC values among the highest of dietary polyphenols)
• Protect endothelial cells from oxidative damage
• Inhibit lipid peroxidation in vascular membranes

Secondary Mechanisms

Retinal microcirculation

• Anthocyanins accumulate in retinal tissue and improve rhodopsin regeneration (in vitro)
• Enhance retinal capillary blood flow and reduce capillary permeability in the retina
• May protect retinal pigment epithelium from oxidative stress

Astringent action (dried fruit)

• High tannin content (condensed tannins / proanthocyanidins) precipitates proteins on mucosal surfaces
• Creates a protective layer that reduces inflammation and fluid secretion
• This is the mechanism for the antidiarrheal and oropharyngeal anti-inflammatory effects

Anti-platelet activity

• Anthocyanins inhibit platelet aggregation via inhibition of phosphodiesterase and thromboxane A2 formation
• This contributes to microcirculatory improvement but also underlies the anticoagulant drug interaction

Clinical Evidence Summary

Volume and Quality of Evidence

• Multiple controlled clinical trials exist, primarily from Italian and French research groups (1970s-2000s)
• Many early studies are of variable methodological quality (small sample sizes, older designs)
• No Cochrane review specifically on bilberry exists
• The most studied preparation is Mirtoselect/Myrtocyan (standardized anthocyanin extract)

Key Clinical Trials

Evidence Assessment

• Vascular indications: Consistent positive signals from multiple controlled trials, though many are older and small; the pharmacological rationale is strong
• Night vision: The popular claim has been largely debunked by modern placebo-controlled trials; Canter & Ernst (2004) systematic review found no support
• Diabetic retinopathy: Promising but insufficient evidence from well-designed modern trials
• Diarrhea: Traditional use well-established; mechanism (tannin astringency) is pharmacologically sound; no modern RCTs specifically testing this indication

European vs US/Anglophone Consensus

Safety Profile

Contraindications

• Known hypersensitivity to Vaccinium myrtillus or Ericaceae family plants
• Bilberry leaf preparations in high doses or long-term use are not recommended (potential toxicity, hydroquinone content)

Drug Interactions

• Anticoagulants/Antiplatelets: Anthocyanins inhibit platelet aggregation; caution with warfarin, heparin, clopidogrel, aspirin, and other anticoagulant/antiplatelet drugs. Monitor INR if co-administered with warfarin
• Antidiabetic agents: Bilberry fruit and leaf may lower blood glucose; monitor in patients on insulin, metformin, or sulfonylureas to avoid additive hypoglycemia
• NSAIDs: Theoretical additive antiplatelet effect

Side Effects

• Generally very well tolerated at recommended doses
• Occasional: mild GI discomfort (nausea, stomach upset)
• Rare: allergic reactions
• Dried fruit at high doses: constipation (due to excess tannin intake)
• Bilberry leaf (not fruit) in chronic high-dose use: potential hydroquinone toxicity (muscle wasting, anemia) — this applies only to leaf preparations

Pregnancy/Lactation

• Fruit consumption: Bilberry fruit as a food is considered safe during pregnancy and lactation
• Concentrated extracts: Insufficient safety data for high-dose anthocyanin supplements during pregnancy; EMA recommends against use due to lack of data
• No teratogenicity reported in preclinical studies

Clinical Dosage

Key point: The dried fruit (rich in tannins) and the fresh fruit extract (rich in anthocyanins) serve different therapeutic purposes. Dried fruit is for diarrhea and mucosal inflammation. Fresh fruit extract standardized to anthocyanins is for vascular indications.

Sources

• German Commission E Monograph: Myrtilli fructus (bilberry fruit, dried)
• ESCOP Monograph: Myrtilli fructus (bilberry fruit)
• EMA/HMPC Assessment Report on Vaccinium myrtillus L., fructus recens and fructus siccus
• Canter PH, Ernst E. Anthocyanosides of Vaccinium myrtillus (bilberry) for night vision — a systematic review of placebo-controlled trials. Surv Ophthalmol. 2004;49(1):38-50
• Colantuoni A, et al. Effects of Vaccinium myrtillus anthocyanosides on arterial vasomotion. Arzneimittelforschung. 1991;41(9):905-909
• Morazzoni P, Bombardelli E. Vaccinium myrtillus L. Fitoterapia. 1996;67(1):3-29
• Perossini M, et al. Diabetic and hypertensive retinopathy therapy with Vaccinium myrtillus anthocyanosides. Ann Ottalmol Clin Ocul. 1987;113:1173-1190

Connections

• Compare with Horse Chestnut and Red Vine Leaf as alternative venoactive phytomedicines for venous insufficiency
• Compare with Hawthorn for cardiovascular flavonoid pharmacology and microcirculatory effects
• Compare with Ginkgo for peripheral vascular indications and microcirculation improvement