A bilberry is a small, dark berry closely related to the blueberry, growing wild across Europe, northern Asia, and parts of western North America. The plant (Vaccinium myrtillus) is a low-growing deciduous shrub that reaches only 4 to 18 inches tall, producing tiny round berries between 5 and 9 millimeters in diameter. What sets bilberries apart from the blueberries you find at the grocery store is what’s inside: cut a bilberry open and the flesh is deep purple all the way through, while a conventional blueberry has pale green or white pulp beneath its blue skin.
How Bilberries Differ From Blueberries
Bilberries and blueberries belong to the same genus, but they look and behave differently on the bush. Bilberry flowers appear alone or in pairs along the stem, while blueberry flowers grow in clusters. Bilberries are smaller, softer, and more intensely pigmented. That deep purple flesh is the most reliable way to tell them apart: if you squish a berry between your fingers and it stains them dark violet, it’s a bilberry.
The flavor tends to be more tart and complex than a typical highbush blueberry, which is one reason bilberries are prized in European cooking. They’re also harder to cultivate commercially. The plants spread through underground stems and form open colonies in the wild rather than growing in the neat, upright bushes that make blueberry farming practical. This means most bilberries are still wild-harvested, which keeps them expensive and relatively uncommon outside of Europe.
Where and When They Grow
Bilberries thrive across a wide range. In Europe, they blanket heathlands, moorlands, and forest floors from Scandinavia through the British Isles and into southern Europe. The species extends across northern Asia and into North America, where it grows east of the Cascades from British Columbia down through the Rockies into New Mexico and Arizona. Populations even exist in southwestern Greenland, believed to have originated from European plants carried across the Atlantic.
The berries ripen in midsummer, typically from late July into August. In many parts of northern Europe, bilberry foraging is a seasonal tradition, with families heading into hillsides and forests to pick by hand. The berries grow low to the ground on slender branches, making harvesting slow work. Special raking tools exist to speed things up, though they can damage the plants.
Why Bilberries Are Unusually Rich in Antioxidants
The same pigment that turns bilberry flesh dark purple is what makes the fruit nutritionally distinctive. Bilberries contain between 300 and 700 milligrams of anthocyanins per 100 grams of fresh fruit, which is higher than strawberries, cranberries, elderberries, sour cherries, and raspberries. Anthocyanins are the plant compounds responsible for red, blue, and purple colors in fruits and vegetables, and they act as potent antioxidants in the body.
Bilberries contain at least 13 different anthocyanins, with delphinidin being the most abundant. When you eat bilberries, these compounds are absorbed into the bloodstream relatively quickly. One study found that specific anthocyanins were detectable in blood plasma within 60 minutes of ingestion. The concentration varies depending on growing conditions, ripeness, and the specific plant, which explains the wide range in reported anthocyanin levels.
The WWII Night Vision Story
You may have heard that British Royal Air Force pilots ate bilberry jam during World War II to sharpen their night vision. It’s a great story, but it’s likely wartime disinformation. Some historians believe the rumor was deliberately spread to prevent the Germans from learning that the British were testing radar equipment on their aircraft. In other versions of the tale, it was carrots, not bilberries, credited with giving pilots superhuman eyesight.
Researchers have since put the claim to the test. Two independent groups, one at the Naval Aerospace Research Laboratory in Florida and another at Tel Aviv University, gave young men either bilberry-derived anthocyanin extracts or a placebo and then measured night visual acuity. Both studies reached the same conclusion: no improvement in night vision. The doses used were equivalent to what someone could reasonably consume from eating berries, so the idea that bilberries boost night vision simply doesn’t hold up.
What the Research Shows for Eye Health
While night vision claims fall flat, bilberries may offer real benefits for a more modern eye problem: screen-related eye fatigue. Several clinical trials have tested bilberry extract in people who spend long hours on phones, tablets, and computers. The results are more encouraging than the night vision data, though still preliminary.
In one trial, 44 adults with digital eye strain took 200 milligrams of bilberry extract daily for six weeks. The supplement reversed measurable changes in how their pupils responded after screen use. Another study found that bilberry extract improved the eye’s ability to shift focus at close range, a function that deteriorates during prolonged near-vision work. Participants in multiple studies reported meaningful reductions in sensations of tired eyes, eye fatigue, and blurred vision after watching movies or playing games on handheld devices for up to an hour.
The proposed mechanism involves anthocyanins helping regenerate a light-sensitive pigment in the retina and improving blood flow to the small muscles that control focus and pupil size. Short-term consumption of bilberry extract has also been shown to increase tear production after four weeks, which could help with the dry eyes that often accompany heavy screen use.
Effects on Blood Sugar and Inflammation
Bilberry’s anthocyanins also show promise for metabolic health. In a controlled study of men with type 2 diabetes managed through diet alone, a single capsule of standardized bilberry extract (equivalent to about 50 grams of fresh berries) reduced both blood sugar and insulin levels after a glucose challenge. That’s a meaningful finding because it suggests bilberry compounds can blunt the blood sugar spike that follows a carbohydrate-rich meal.
The anti-inflammatory effects are also notable. When people with features of metabolic syndrome ate the equivalent of 400 grams of fresh bilberries daily for eight weeks, markers of low-grade inflammation dropped significantly. In another trial, 120 healthy volunteers who took anthocyanins from bilberries and black currants for just three weeks showed reduced levels of several inflammatory markers in their blood. Longer supplementation over 24 weeks lowered LDL cholesterol and raised HDL cholesterol in people with high cholesterol, alongside further reductions in inflammation.
How Bilberries Are Used
In Scandinavian and northern European cooking, bilberries appear in jams, pies, sauces, and cordials. They pair well with cream-based desserts and game meats. Fresh bilberries are fragile and stain everything they touch, so they’re often frozen, dried, or made into preserves shortly after picking. The intense flavor means a small amount goes a long way compared to milder cultivated blueberries.
As a supplement, bilberry extract is typically standardized to contain 36% anthocyanins by weight. A standard capsule of about 0.47 grams of this extract delivers roughly the anthocyanin equivalent of 50 grams of fresh fruit. Most clinical trials have used between 20 and 300 milligrams of extract daily, with treatment periods ranging from three weeks to six months.
Safety Considerations
Bilberries eaten as food are safe for most people. As a concentrated supplement, there are a few interactions worth knowing about. Bilberry can affect how blood clots, which creates potential problems if you take blood thinners like warfarin, aspirin, or common anti-inflammatory painkillers like ibuprofen. In one reported case, a 77-year-old man on blood thinners experienced rectal bleeding and blood in his urine while also taking bilberry. The combination can amplify bleeding risk.
Because bilberry extracts can lower blood sugar, people taking diabetes medications should be aware that the two effects could stack, potentially pushing blood sugar too low. This isn’t a concern with the small amounts found in foods, but concentrated supplements deliver a much larger dose of active compounds than you’d get from a handful of berries.