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. Bilberry anthocyanins are thought to regenerate rhodopsin, a pigment in retinal photoreceptor cells, and bilberry has been used for poor night vision, macular degeneration, glaucoma, and cataracts.
In vitro, isolated bilberry polyphenols appear to protect against neurodegenerative processes and eye disorders (1) (2). Animal models suggest the 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, and retinal function (5) (6) and 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).
A standardized bilberry extract was shown to reduce disease activity in a pilot study of 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 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 also 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 bilberry extract may significantly reduce proliferation of colorectal cancer tumor tissue (22). Bilberry extract has 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 this effect. More studies are needed to determine what benefits are attributable to bilberry fruit itself, as well as its potential synergy with other berry compounds and food combinations.