Scientific Name(s): Fructus myrtilli, Vaccinium myrtillus L.
Common Name(s): Bilberry , Bog bilberry, Heidelbeere, Huckleberry, Whortleberry
Drug class: Herbal products
Medically reviewed by Drugs.com. Last updated on Aug 13, 2021.
Clinical studies are limited. Interest has focused on antioxidant potential in cancer and cardiovascular conditions, and other applications may exist in diabetes, as well as in inflammatory bowel and ocular conditions.
Typical bilberry products are standardized to 25% anthocyanoside content, and 100 g of fresh fruit contains anthocyanin content 300 to 700 mg. Limited clinical studies have evaluated supplemental bilberry 100 to 500 g over 1 to 8 weeks’ duration.
Contraindications have not yet been identified.
Generally recognized as safe (GRAS) when used as food. Avoid doses above those found in food because safety and efficacy are unproven.
None well documented.
Information is lacking.
Information is lacking. Long-term use of bilberry leaves is suspected to lead to adverse effects.
- Ericaceae (heath)
The bilberry plant originates from Europe and has been naturalized in the North American Rocky Mountains. The small deciduous shrub differs from the North American blueberry (Vaccinium corymbosum and Vaccinium angustifolium) and grows best in shady, moist conditions. The plant bears bluish-black berries that are 5 to 9 mm in diameter and contain many small, shiny brownish-red seeds that are somewhat caustic and sweet-tasting. The bright green leaves are short, petiolate, and elliptic to round, and are 10 to 30 mm long.1, 2, 3 Other Vaccinium species include cranberries, blueberries, and whortleberries.
Traditional uses of dried bilberry fruit include supportive treatment of short-term, nonspecific diarrhea when administered as a tea, and as a topical decoction for inflammation of the mucous membranes of the mouth and throat. Folkloric use of the berries in cough preparations in the 15th century and use in diabetes at the end of the 19th century has been reported.
During World War II, British Royal Air Force pilots ate bilberry preserves before night missions in the belief that bilberry would improve their vision. Some European health care providers later recommended bilberry extracts for other eye complaints.2, 4, 5
Bilberry fruit consists of up to 10% tannins, most of which are catechol tannins. In addition, the fruit contains at least anthocyanins, flavonoids, organic and phenolic acids, invert sugars, and pectins. Triterpenoids, steroids, triterpenes, and esters have been elucidated in the fruit by processes such as high-pressure liquid chromatography.2, 6, 7, 8, 9 The leaves of the bilberry plant contain large amounts of chromium.6
Anthocyanin content of the fruit varies with geographical location, as well as growing and processing conditions,3, 7, 9 and is greater than that found in strawberries, cranberries, elderberries, and sour cherries.6
Uses and Pharmacology
Bilberry anthocyanins are natural antioxidants (scavengers and chelators), and in vitro studies have shown protective effects against oxidative damage. Animal studies, however, have produced conflicting data, with some studies demonstrating a protective effect and others showing no effect on oxidative markers.10, 11, 12, 13
Studies among healthy volunteers suggest no effect of bilberry on lipid peroxidation.6, 14 Despite fresh bilberries being a rich source of anthocyanins, and thus of antioxidants, variation in the content of commercial preparations has been noted as well lack of standardization, which must be considered in extrapolating antioxidant activity to clinical benefits.2, 3, 6, 14
Oral, topical, and intravenous bilberry administration have demonstrated an anti-inflammatory response in rodents and rabbits. Interruption of the inflammatory response, interference with proinflammatory mediators, antioxidant action, and direct effects on mast cell degradation have been reported to be responsible for reductions in pruritus and swelling in mice with induced contact allergic dermatitis.2, 6, 15, 16, 17
Preliminary data in recreationally trained runners reflected possible negative effects related to short-term consumption of bilberry juice as observed by moderate, transient increases in muscle soreness and inflammation.54 Information regarding the use of bilberry in the treatment of allergies is limited.
In vitro studies using human colon cancer cells lines suggest bilberry extract might interfere with topoisomerase in protecting DNA. Anti-inflammatory and antioxidant actions have also been suggested as mechanisms for observed reductions in rat intestinal adenoma and induced retinopathy. Reduced angiogenesis has also been observed in vitro.6, 18, 19, 20
A pilot study conducted in patients with colorectal cancer used bilberry anthocyanins 0.5 to 2 g daily for 7 days before surgery and found a decreased rate of proliferation of cancerous tissue. Metabolites of the bilberry anthocyanins were found in the tumor tissue.6
In vitro studies and data from animal models and experiments suggest bilberry extract or its chemical constituents are able to inhibit smooth muscle contraction, platelet aggregation, ischemic perfusion injury, and vascular permeability.2, 6, 21, 22, 23
Limited, small studies among participants with elevated cardiovascular disease risk factors have found a decrease in C-reactive protein and other inflammatory markers, including interleukin-6.6, 14, 24 The studies evaluated supplemental bilberry 100 to 400 g over 4 to 8 weeks.6, 24 In overweight participants, decreased weight was accompanied by improvements in vascular cell adhesion and brachial flow mediated dilation, but effects were equivocal on the lipid profile.6, 25, 26, 46
In vitro studies on rodent pancreatic cells have shown increased insulin secretion and glucose transport, postulated to be consequent to an effect on alpha-glucosidase.6 Studies in mice with induced diabetes consistently report decreased plasma glucose and increased insulin sensitivity with extracts of bilberry leaves (high in chromium content).5, 6, 27 Older studies were also reported in cats, rabbits, and dogs.5
Studies in diabetic patients are lacking; older studies lack adequate methodological robustness.5, 6 Studies in participants with elevated cardiovascular disease risk factors have shown small25 to no changes6, 24 in plasma glucose or insulin. In the Sysdimet (Dietary Modulation of Gene Expression and Metabolic Pathways in Glucose Metabolism) study, a combination of whole-grain foods, fish oils, and bilberries improved glucose metabolism.28
Mice with induced acute colitis that were fed bilberries or anthocyanins showed improved histological outcomes; however, efficacy in chronic colitis was not as important.29 Bilberries showed a protective action against induced gastric ulcers in mice.30
Despite folklore use of bilberries for diarrhea, limited clinical trials have been reported. Open-label, pilot studies have been conducted in patients with mild to moderate colitis31 and with diarrhea-associated irritable bowel syndrome.32 The majority of patients consuming anthocyanin-rich bilberry extract showed a positive response; however, these studies need to be confirmed using blind, randomized, controlled protocols.
Studies in mice suggest bilberry exerts a protective effect against induced-retinal inflammation and uveitis6, 33, 34 and may play a role in upregulation of crystallins induced by a high-fat diet and, therefore, may be relevant to diabetic retinopathy.35 Corneal epithelial cells showed increased cell viability in the presence of bilberry extract.36
Results from early clinical studies conducted on pilots in World War II have not been replicated in more recent, small clinical trials.2, 6 An experiment conducted among United States Navy SEALs found no difference in night vision acuity or contrast sensitivity after 3 weeks (standardized to 25%) of supplemental bilberry extract 160 mg.2 Other clinical studies have used combinations of bilberry and vitamin E.2, 6 Improved measures of visual acuity were reported after a mean duration of 24 months of supplemental bilberry anthocyanins 120 mg in glaucoma-free participants versus placebo.37 Further clinical trials may be warranted.6 A small, 4 week study of 200 mg daily of fermented billberry extract conducted in middle-aged, myopic patients found significant improvement in mean amplitude of accommodation mesopic contrast sensitivity.47
Objective and subjective measurements of video display-induced eye fatigue were evaluated in a prospective, randomized, double-blind, placebo-controlled trial that administered bilberry extract (480 mg/day) for 8 weeks to Japanese office workers who complained of eye fatigue caused by use of video display terminals. Objective ophthalmic signs were assessed by measuring critical flicker fusion (CFF) and near point accommodation (NPA), whereas subjective symptoms were assessed through a self-reported questionnaire. Bilberry extract supplements (480 mg/day) or placebo were administered once daily after breakfast. At 8 weeks, the range of variation in CFF was significantly reduced in only the bilberry group; however, the difference in reduction range between groups was not significant. No difference in NPA was observed. Subjective symptoms improved significantly within the bilberry group as well as compared to placebo. At 8 weeks, dry eye sensation, double vision, and uncomfortable sensation all improved compared to baseline with bilberry (P < 0.05). Additionally, variations and eye fatigue (eg, ocular fatigue sensation, ocular pain, uncomfortable sensation, foreign body sensation) were significantly improved compared to placebo as early as week 4. Minor adverse events were reported in both groups; less frequent effects that occurred with bilberry included gastritis and gastric distress.49
A clinical study from 1985 reported symptomatic improvement in dysmenorrhea with anthocyanosides 115 mg/day.2 Bilberry reduced bacterial adhesion to a lesser extent than cranberry and showed efficacy against Streptococcus pneumoniae and Staphylococcus aureus.38 Bilberry showed a dose-dependent effect on periods of immobility in mice with stress-induced chronic depression, suggested to be related to an antioxidant action.12
The effect of bilberry supplementation on routine dental clinical parameters of inflammation was evaluated in a randomized placebo-controlled trial in 24 healthy adults. Participants received standard of care (debridement and oral hygiene instructions), placebo, or 1 of 2 doses of bilberries 250 g/day or 500 g/day for 7 days. The 500 g/day bilberry and standard of care groups experienced a similar mean reduction in bleeding on probing (59% and 58%, respectively), while the lower dosed bilberry group and placebo group exhibited a 41% and 31% reduction, respectively. The difference between the 500 g/day bilberry group and placebo group was statistically and clinically significant. Additionally, significant differences were also observed in 3 cytokines (interleukin [IL]-1-beta, IL-6, and vascular endothelial growth factor) in the higher dose bilberry group compared to baseline. No adverse events were reported.48
Traditional dosages range from dried berries 20 to 60 g /day, or fresh berries 100 to 300 g/day.39
Typical bilberry products are standardized to 25% anthocyanoside content (approximately 36% anthocyanin), and 100 g of fresh fruit contains between 300 to 700 mg anthocyanin.6
Pregnancy / Lactation
GRAS status when used as food. Avoid doses above those found in food because safety and efficacy are unproven.
Agents with Antiplatelet Properties: Herbs (Anticoagulant/Antiplatelet Properties) may enhance the adverse/toxic effect of Agents with Antiplatelet Properties. Bleeding may occur. Consider therapy modification.40, 41, 42, 43, 50, 52
Herbs (Anticoagulant/Antiplatelet Properties): May enhance the adverse/toxic effect of other Herbs (Anticoagulant/Antiplatelet Properties). Bleeding may occur. Consider therapy modification.40, 41, 42, 43, 50, 52
Hypoglycemic Agents: Herbs (Hypoglycemic Properties) may enhance the hypoglycemic effect of Hypoglycemic Agents. Monitor therapy.44
Nonsteroidal Anti-Inflammatory Agents: Herbs (Anticoagulant/Antiplatelet Properties) may enhance the adverse/toxic effect of Nonsteroidal Anti-Inflammatory Agents. Bleeding may occur. Consider therapy modification.40, 41, 42, 43, 50, 52
Thrombolytic Agents: Herbs (Anticoagulant/Antiplatelet Properties) may enhance the adverse/toxic effect of Thrombolytic Agents. Bleeding may occur. Consider therapy modification.40, 41, 42, 43, 50, 52
Information regarding adverse reactions with the use of bilberry is limited.
Mutagenicity has not been observed.6 The plant's leaves are not approved for therapeutic use in German Commission E Monographs. Long-term use of bilberry leaves is suspected to be hazardous.45 No cytotoxic effect was seen on corneal epithelial cells exposed to bilberry extract.36 Low concentrations of bilberry extract were protective in animal models of reperfusion injury; however, high concentrations increased sequelae of the reperfusion injury.21
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