- Dwarf bilberry
- European blueberry; whortleberry
- Bog bilberry
- Chinese blueberry
For Patients & Caregivers
How It Works
Bilberry is used in traditional medicine to treat eye disorders and support vision health, but clinical data for these purposes are mixed or lacking. There is insufficient evidence to support its other uses.
Compounds in bilberry called anthocyanins can regenerate rhodopsin, a pigment found in retinal cells responsible for eyesight. This is one of the reasons it has gained popularity in traditional medicine to support eye health.
In laboratory studies, bilberry reduces inflammation and fluid accumulation in tissues, acts as an antioxidant, inhibits blood clotting, and strengthens the walls of blood vessels. Bilberry extracts can inhibit the growth of cancer cells in the lab. Initial studies in humans also show that bilberry may have anti-cancer effects, relieve certain types of inflammation, or improve the biological profiles of those at higher risk for heart disease or diabetes. More clinical trials are needed to confirm these effects.
- To prevent cancer
Laboratory studies and one clinical study suggest anti-cancer effects. More studies are needed.
- To treat eye disorders
One small study suggests bilberry may improve visual function in some patients with normal tension glaucoma, but human data are generally lacking. The effect of bilberry on other eye conditions has been explored in animal and test tube studies, or in older studies with weak trial designs.
- To reduce inflammation
A few preliminary studies suggest that bilberry may be helpful in preventing or treating gastrointestinal mucositis, or for those with mild to moderate ulcerative colitis. Other small studies indicate that bilberry may improve biomarkers of inflammation related to cardiovascular disease. Larger confirmatory studies are needed.
- To improve vision, especially at night
Clinical trial results are mixed on whether bilberry can help improve vision, and do not support this use in individuals with good vision.
- To treat diarrhea
No scientific evidence supports this specific use, although one small study indicates bilberry may be helpful in mild to moderate ulcerative colitis.
- To treat circulatory disorders
Laboratory studies show that bilberry may protect blood vessels and decrease the risk of blood clots. Human data are needed.
Do Not Take If
For Healthcare Professionals
Bilberry fruit grows on perennial fruit trees or shrubs, and is closely related to the huckleberry and blueberry. It is marketed as a dietary supplement to help improve eyesight and promote overall eye health, and is widely used in herbal therapy. The anthocyanins in bilberry are thought to regenerate rhodopsin, a pigment present in retinal photoreceptor cells.
In vitro, bilberry polyphenols appear to protect against neurodegenerative processes and eye disorders (1) (2). Animal models suggest bilberry extract may help visual functioning (3) and protect against retinal diseases (4). Human studies are mixed on whether bilberry anthocyanosides improve visual acuity, night vision, or retinal function (5) (6) ; many of the positive studies are poorly designed (7). A small trial suggests bilberry may improve visual function in some individuals with normal tension glaucoma (8), but generally human data on bilberry for eye disorders are lacking (9).
In other studies, a standardized bilberry extract was shown to reduce disease activity in patients with mild to moderate ulcerative colitis (10). Dietary bilberry produced beneficial changes in serum lipids and lipoproteins in women with higher metabolic risk, but had an unexpected opposite effect in those who were at low risk (11). Another species of bilberry, Caucasian whortleberry, was found to improve glycemic control in type 2 diabetic patients (12). Ingestion of bilberries in a diet that also included whole grain/low-insulin-response grain products and fatty fish altered lipid profiles and improved glucose metabolism in individuals at high risk for type 2 diabetes (13). Two small randomized trials suggest that bilberry juice may reduce biomarkers of inflammation and improve cardiometabolic risk (14) (15).
In vitro and in vivo studies indicate that bilberry may have anticancer activities (4) (16) (17) (18) (19) (20) (21). A pilot study suggests that bilberry extract may significantly reduce proliferation of colorectal cancer cells (22). Bilberry extract also showed a protective effect against chemotherapy-induced oral mucositis in an animal model (23). Other small studies of a proprietary extract combination that includes bilberry suggests it may relieve chemotherapy-induced mucositis in cancer patients (24) (25). However, it is unclear the extent to which bilberry itself may be responsible for such effects. More studies are needed to determine what benefits are attributable to bilberry fruit, as well as its potential synergy with other berry compounds and food combinations.
Mechanism of Action
In vitro, bilberry polyphenols inhibited amyloid fibril formation and dissolved preformed toxic aggregates and mature fibrils, suggesting a role in controlling fibril formations of various proteins that occur with neurodegenerative diseases (1). Bilberry anthocyanins modulated oxidative stress defense enzymes heme oxygenase-1 (HO-1) and glutathione S-transferase-pi (GST-pi) in human retinal pigment epithelial cells (2). In vitro and in vivo, bilberry inhibited angiogenesis through inhibition of ERK 1/2 and Akt phosphorylation (4). In an animal model of uveitis and retinal inflammation, pretreatment with a bilberry extract prevented photoreceptor impairment, relieved intracellular ROS elevation, activated retinal NF-ĸB in the inflamed retina, and suppressed the decrease of rhodopsin via inhibition of IL-6, which activates STAT3, thereby protecting outer segment length in photoreceptor cells (3). In a monocytic cell line, quercetin, epicatechin, and resveratrol inhibited lipopolysaccharide (LPS)-induced NF-kappaB activation (14).
In individuals with hypercholesterolemia, anthocyanins may improve endothelium-dependent vasodilation by activating the NO-cGMP signaling pathway (28). The polyphenols in bilberry juice can modulate inflammation by decreasing plasma C-reactive protein, interleukin (IL)-6, -15, and monokine induced by INFγ (MIG) (14).
In human colon and liver cancer cell lines, bilberry anthocyanins demonstrated intracellular antioxidant activity even though concentrations applied were very low (29). Bilberry extract inhibited human leukemia, colon, and breast cancer cells through apoptotic induction and/or inhibition of cell proliferation (17) (30). Delphinidin and other anthocyanidins synergistically enhanced cell-cycle arrest and apoptotic induction in aggressive non-small-cell lung cancer cells by modulating Notch, WNT, and NF-ĸB signaling pathways (16).
Rectal bleeding following long-term overconsumption of bilberry has been reported in a 77-year-old man on warfarin therapy, requiring two emergency room visits, treatment with fresh plasma infusions, and hospitalization to evaluate inconsistent international normalized ratio (INR) values (33) (34).
Anticoagulants / Antiplatelets: Bilberry may potentiate the risk of bleeding (33) (34).
Aspirin and aspirin products: Bilberry can have added or synergistic antiplatelet effects, and increase the risk of bleeding (35).
Non-steroidal anti-inflammatory drugs (NSAIDs): Bilberry may have added or synergistic antiplatelet effects, and increase the risk of bleeding (35).
Chemotherapy drugs: Bilberry may interfere with the actions of certain chemotherapy drugs and radiation therapy (25) .