A bilberry is a small, dark-purple berry native to northern Europe and parts of Asia, closely related to the common blueberry but notably richer in plant pigments called anthocyanins. Its scientific name is Vaccinium myrtillus, and it grows wild on low shrubs in forests and heathlands rather than being widely cultivated on farms. Bilberries have a long history in European folk medicine, particularly for eye complaints, and modern research has started to test those traditional claims with mixed but often encouraging results.
How Bilberry Differs From Blueberry
Bilberry and the cultivated highbush blueberry (Vaccinium corymbosum) belong to the same genus, and they look similar enough to confuse shoppers. The differences show up once you cut one open: a blueberry has pale green or white flesh, while a bilberry is dark red or purple all the way through. That interior color matters because it reflects a much higher concentration of anthocyanins, the pigments responsible for most of the berry’s studied health effects. Analyses comparing the two have found that total phenolic content is higher in wild bilberry, and bilberry scored the highest total antioxidant capacity among the Vaccinium species tested.1Turkish Journal of Biology. A comparison of major taste- and health-related compounds of Vaccinium berries
The berries are also smaller and softer than blueberries, making them harder to ship fresh. That fragility is one reason bilberries are rarely found in North American grocery stores. Most of the world’s bilberry supply is wild-harvested in Scandinavian and Eastern European forests, which contributes both to the berry’s appeal as a “wild” food and to concerns about sustainability and consistent quality.
What Makes Bilberry Nutritionally Distinctive
Bilberry’s reputation rests largely on its anthocyanin content. Wild bilberries contain between roughly 236 and 656 milligrams of total anthocyanins per 100 grams of fresh fruit, with the wide range reflecting growing conditions like altitude, sunlight, and soil.2Journal of Food Composition and Analysis. Variations in polyphenol content and anthocyanin composition in bilberry populations (Vaccinium myrtillus L.) due to environmental factors Delphinidin-based anthocyanins are the most abundant type, followed by cyanidin types. Beyond anthocyanins, the fruit contains flavonols, phenolic acids, carotenoids, vitamin C, and tocopherols.3PubMed Central. A Review of Major Compounds in Bilberry (Vaccinium myrtillus L.) Fruits and Leaves: Isolation, Purification, and Their Antiaging Effects
The environmental sensitivity of bilberry’s chemistry is worth knowing if you buy bilberry products. Two batches of wild-picked berries from different forests or different years can vary dramatically in their anthocyanin load. A bilberry supplement standardized to a specific anthocyanin percentage is an attempt to smooth out that natural variation, though standardization itself introduces its own problems, discussed below.
Eye Health and Vision
The connection between bilberry and eyesight is the oldest and most recognized claim. British Royal Air Force pilots during World War II supposedly ate bilberry jam before nighttime missions, though that story is more legend than documented science. Modern research has put the idea through controlled trials with results that are promising in some areas but underwhelming in others.
For everyday eye fatigue, particularly the kind caused by long hours in front of a screen, bilberry supplementation has shown real effects. In one randomized, double-blind trial, workers who took 480 milligrams of bilberry extract daily for eight weeks experienced less eye fatigue, less eye pain, and less of the heavy-eye sensation that comes with prolonged screen use, compared to a placebo group.4The Journal of nutrition, health and aging. Bilberry extract supplementation for preventing eye fatigue in video display terminal workers A separate trial using 240 milligrams of standardized bilberry extract found that after 12 weeks, the ciliary muscle (the tiny muscle that adjusts your eye’s focus) worked measurably better during close-up tasks and screen work.5PubMed Central. A 12-Week-Long Intake of Bilberry Extract (Vaccinium myrtillus L.) Improved Objective Findings of Ciliary Muscle Contraction of the Eye
For more serious eye conditions, the picture is murkier. A study in patients with normal-tension glaucoma found that bilberry anthocyanins improved visual acuity and visual field measurements, but this was a small trial.6PubMed Central. Ginkgo biloba extract and bilberry anthocyanins improve visual function in patients with normal tension glaucoma Early studies on diabetic retinopathy reported improvements in retinal blood vessel health, but reviews of those older trials have flagged serious methodological problems. One year-long study in diabetic retinopathy patients found improved contrast sensitivity but no change in other important markers like visual acuity or microaneurysms.7Frontiers in Pharmacology. Bilberries: Curative and Miraculous – A Review on Bioactive Constituents and Clinical Research A combination of bilberry extract (standardized to 36% anthocyanins) and French maritime pine bark extract lowered elevated intraocular pressure in patients almost as effectively as a standard prescription drug, though it took six months rather than one month to reach comparable effect.
The honest summary: bilberry appears to help with everyday eye strain and fatigue, which is the problem most people actually have. For serious eye diseases, the data is thin and the trial quality is often poor. If you have glaucoma or diabetic retinopathy, bilberry is not a substitute for medical treatment.
Blood Sugar Regulation
Bilberry’s effects on blood sugar are one of the more interesting areas of current research. In a human trial, overweight volunteers who consumed an anthocyanin-enriched bilberry extract for three weeks showed about a 20% reduction in the blood sugar spike that follows a glucose load, without any change in insulin levels.8Journal of Functional Foods. Anthocyanin-enriched bilberry extract attenuates glycaemic response in overweight volunteers without changes in insulin The fact that insulin stayed the same suggests the effect works by slowing down how fast carbohydrates are broken down or absorbed in the gut, rather than by boosting insulin production.
Animal studies have found a complementary mechanism: in diabetic mice, a bilberry-enriched diet activated an energy-sensing enzyme called AMPK in fat tissue, muscle, and the liver, which improved both blood sugar levels and insulin sensitivity.9PubMed. Dietary anthocyanin-rich bilberry extract ameliorates hyperglycemia and insulin sensitivity via activation of AMP-activated protein kinase in diabetic mice These are mouse data and cannot be directly translated to human doses, but the direction of the findings lines up with the human trial evidence. If you already take blood-sugar-lowering medication, adding bilberry supplements is something to discuss with your doctor, since the combined effect could theoretically push blood sugar too low.
Cardiovascular and Anti-Inflammatory Effects
Bilberry anthocyanins have been tested for their effects on blood vessels. In lab experiments using porcine coronary arteries (a common stand-in for human arteries), an anthocyanin-rich bilberry extract caused the artery walls to relax in a dose-dependent way, an effect that depended on the endothelium, the thin inner lining of blood vessels.10PubMed. Direct vasoactive and vasoprotective properties of anthocyanin-rich extracts Blood vessel relaxation like this is associated with lower blood pressure and better blood flow, though demonstrating the same magnitude of effect in living humans after oral consumption is a different challenge.
The anti-inflammatory angle adds another layer to bilberry’s potential cardiovascular relevance. Cell and animal studies have shown that bilberry reduces the expression of several inflammatory markers, including TNF-alpha, IL-6, and IL-1beta, and modifies the signaling pathways that drive chronic low-grade inflammation.11PubMed Central. Anti-Inflammatory Activity of Bilberry (Vaccinium myrtillus L.) Since chronic inflammation is a recognized driver of cardiovascular disease, these mechanisms are biologically plausible. But most of this evidence comes from cell cultures and animal models. Large-scale human cardiovascular outcome trials with bilberry have not been conducted.
Gut Health
One of the newer and more compelling lines of bilberry research involves the gut microbiome. In aging rats, bilberry anthocyanin extract promoted the growth of beneficial intestinal bacteria while suppressing harmful ones, and these changes correlated with improvements in the intestinal mucosal barrier, the lining that keeps gut contents from leaking into the bloodstream.12PubMed. Bilberry anthocyanin extract promotes intestinal barrier function and inhibits digestive enzyme activity by regulating the gut microbiota in aging rats
In a separate study, rats fed a high-fat diet developed signs of gut dysbiosis, including the expansion of potentially harmful bacteria in the Enterobacteriaceae family. Adding bilberry to that high-fat diet prevented the microbial disruption and counteracted the diet-induced increase in an inflammatory enzyme in the colon lining.13PubMed. High-Fat Diet Enriched with Bilberry Modifies Colonic Mucus Dynamics and Restores Marked Alterations of Gut Microbiome in Rats These are animal findings, but they tie in with an important observation about how bilberry anthocyanins are absorbed: a substantial portion of the anthocyanins you eat are never absorbed in the upper gut. About 30% of ingested bilberry anthocyanins survive intact through the small intestine, meaning they reach the colon, where they feed microbes and get metabolized into other bioactive compounds.14Food Chemistry. Human intervention study to investigate the intestinal accessibility and bioavailability of anthocyanins from bilberries The colon may actually be a more important site for bilberry’s health effects than the bloodstream.
How Well Your Body Absorbs Bilberry Anthocyanins
A recurring challenge in anthocyanin research is bioavailability, meaning how much of what you swallow actually reaches your blood and tissues. The numbers are low. In rats given bilberry extract orally, the overall bioavailability of the anthocyanin mixture was under 1%, with individual anthocyanins ranging from about 0.6% to 1.8%.15PubMed. Bioavailability and tissue distribution of anthocyanins in bilberry (Vaccinium myrtillus L.) extract in rats Anthocyanins appear in the blood quickly, peaking within 15 to 30 minutes of ingestion, but they also disappear fast.16Journal of the Science of Food and Agriculture. Bioavailability of a bilberry anthocyanin extract and its impact on plasma antioxidant capacity in rats
This sounds discouraging until you consider two things. First, anthocyanins are converted into other compounds (glucuronides and various breakdown products) that also enter the bloodstream and are themselves biologically active. In a human study, higher amounts of these degradation products reached the circulation than intact anthocyanins did.14Food Chemistry. Human intervention study to investigate the intestinal accessibility and bioavailability of anthocyanins from bilberries Second, as mentioned above, the colon appears to be a major site for absorption. People with an intact colon had substantially higher plasma levels of both anthocyanins and their breakdown products than people who had undergone ileostomy surgery, confirming that the large intestine plays a big role in extracting value from these compounds.
Skin Benefits
Bilberry has entered the skincare conversation through both topical and oral routes. In a cell study, bilberry extract applied to human skin cells (keratinocytes) before or after UVA exposure reduced the formation of reactive oxygen species and prevented damage to cell membranes, effects attributed to the anthocyanin content.17PubMed. Bilberry extract reduces UVA-induced oxidative stress in HaCaT keratinocytes: a pilot study
A human trial tested a fermented bilberry extract taken orally over 84 days in a randomized, double-blind, placebo-controlled design. By the end of the trial, participants in the bilberry group showed measurable improvements: wrinkle depth decreased by about 11%, skin elasticity improved by about 12%, skin antioxidant capacity increased by roughly 21%, and skin lightness increased slightly while redness decreased by about 17%.18PubMed Central. Antiaging, Brightening, and Antioxidant Efficacy of Fermented Bilberry Extract (Vaccinium myrtillus): A Randomized, Double-Blind, Placebo-Controlled Trial These are statistically meaningful differences compared to the placebo group, though whether they are visible to the naked eye is another question.
Safety and Side Effects
Bilberry has a strong safety profile for a supplement. In laboratory testing on neuronal cells, bilberry extract showed no toxic effects even at concentrations up to 4,000 micrograms per milliliter.19Frontiers in Nutrition. In vitro mechanistic studies and potential health benefits of a standardized bilberry extract in low mood and cognitive enhancement In the human trials cited throughout this article, side effects were generally not reported as a significant issue.
That said, there are practical concerns to keep in mind:
- Blood sugar interaction: Because bilberry can lower post-meal blood sugar, anyone taking diabetes medication or insulin should be cautious about combining the two without medical guidance.
- Bleeding risk: Some sources suggest that bilberry anthocyanins have mild antiplatelet effects. If you take blood thinners or are scheduled for surgery, mention bilberry supplements to your doctor.
- Digestive upset: High doses of any anthocyanin-rich food can cause mild stomach discomfort or loose stools in some people, though this is not specific to bilberry.
- Pregnancy and breastfeeding: There is not enough human data to confirm safety during pregnancy or breastfeeding, so most guidelines recommend caution.
Fresh Fruit Versus Processed Products
If you can get fresh bilberries, those will have the highest anthocyanin content. But fresh bilberries are seasonal and perishable, so most people encounter them in processed form. A study comparing different bilberry products found that fresh fruit had the highest total anthocyanins (about 5,190 milligrams per 100 grams on a dry-weight basis), followed by puree, infusion, and liqueur. Fresh and pasteurized juices came in lowest, at roughly 921 and 1,099 milligrams per 100 grams dry weight respectively.20PubMed. Are Processed Bilberry Products a Good Source of Phenolics? The drop from fresh fruit to juice is dramatic. Still, even processed bilberry products retain meaningful levels of phenolic compounds and remain a useful source year-round.
Dried bilberry powder and concentrated extracts, which are the forms used in most supplements, go through their own processing steps that can affect potency. Standardized extracts typically aim for an anthocyanin content of 25% to 36%, which is far more concentrated than eating the fresh fruit. This concentration is why supplement studies often use doses in the 160-to-480-milligram range of extract rather than telling participants to eat a cup of berries.
The Adulteration Problem
Because wild bilberry is expensive and supply is limited, the supplement market has a significant adulteration problem. One analytical study found that roughly half of the bilberry extracts tested differed so much from reference bilberry that adulteration was suspected. About 60% of the extracts and a third of finished food supplements contained less anthocyanin than their labels claimed. The most common adulterants were cheaper berries like mulberry and chokeberry, which have similar color but different anthocyanin profiles.21PubMed. Bilberry adulteration: identification and chemical profiling of anthocyanins by different analytical methods
A separate study analyzing 71 commercial bilberry extracts confirmed the issue, identifying six outright counterfeits and finding that authentic extracts had anthocyanin content in the 18-to-34% range.22Journal of Spectroscopy. Near-Infrared Spectroscopy and Chemometrics for the Routine Detection of Bilberry Extract Adulteration and Quantitative Determination of the Anthocyanins If you are buying bilberry supplements, third-party testing certifications matter more here than for many other botanicals. Look for brands that provide certificates of analysis or carry seals from independent testing labs.
Bilberry in the Wild
Bilberry plants are a cornerstone species in northern European forest ecosystems, providing food for birds, bears, and other wildlife. Because nearly all bilberry is wild-harvested rather than cultivated, the ecological impact of commercial picking is a real concern. Forestry practices have a large influence on whether bilberry thrives. Clear-cutting sharply reduces bilberry abundance, and while some recovery can begin within a decade on drier sites, it typically takes 60 to 80 years for bilberry cover in production forests to return to levels seen in old-growth forests.23Forest Ecology and Management. Disentangling the effects of seminatural forestry on an ecosystem good: Bilberry (Vaccinium myrtillus) in Estonia Retaining some trees during harvesting only slightly softens the blow. In Scandinavian countries, where bilberry picking is protected under “everyman’s right” laws that allow public foraging on private land, balancing commercial-scale harvesting with ecosystem health is an ongoing policy conversation.
Climate change adds another layer of uncertainty. Bilberry plants are adapted to cool, humid forest conditions, and their growth and fruit production are sensitive to factors like canopy density, soil moisture, and temperature. Research in Central European forests has found significant variability in bilberry plant health depending on local forest conditions, with populations classified along a spectrum from prosperous to depressed based on factors like total leaf area and plant height.24ScienceDirect. Size and vitality characteristics of bilberry (Vaccinium myrtillus L.) populations in the Central Bohemian region of the Czech Republic As forests change under warming conditions, the geography and abundance of wild bilberry are likely to shift as well, which would ripple through both the supplement industry and the ecosystems that depend on the plant.