Bilberry is a small, dark purple berry native to Northern Europe that has attracted considerable interest for its high anthocyanin content. These berries—sometimes called European blueberries—contain significantly more anthocyanins than their North American cousins, and this difference has made bilberry a popular ingredient in eye health supplements across the globe.

But does the science actually support the traditional uses of bilberry? And what should you know before taking a supplement? I’ve dug through the clinical research to separate genuine findings from marketing hype.

What is bilberry?

Bilberry (Vaccinium myrtillus) is a low-growing shrub that thrives in the acidic soils of Northern and Central Europe, though it also grows in parts of North America and Asia. The small fruits measure about 5 to 9 mm in diameter and have a distinctive blue-black colour with deeply pigmented flesh.

The fruit contains a variety of plant polyphenols including anthocyanins, flavonols, quercetin, catechins, ellagitannins, and phenolic acids. Among these, anthocyanins are the most abundant and have become the primary focus of scientific research. These compounds are responsible for the berry’s deep purple colour and are thought to provide antioxidant and anti-inflammatory effects 1.

In traditional medicine, bilberry has been used for conditions ranging from diarrhoea and gastrointestinal complaints to eye fatigue, night vision problems, and circulatory disorders. The British Royal Air Force pilots during World War II famously claimed that eating bilberry jam improved their night vision—though as we’ll see, this particular benefit hasn’t held up under scientific scrutiny.

How is bilberry different from blueberry?

People often confuse bilberry with blueberry, which is understandable given their similar appearance. However, there are several key differences worth noting.

Appearance: Bilberries are smaller and darker than blueberries. The most obvious difference is inside—bilberry flesh is deep blue or purple throughout, whilst blueberry flesh is pale green. Blueberries also have a distinct star-shaped calyx at the end.

Anthocyanin content: Bilberries contain between 300 and 700 mg of anthocyanins per 100 grams of fresh fruit, depending on variety, growing conditions, and ripeness. This is considerably higher than most blueberry varieties 2.

Other compounds: Blueberries tend to have higher levels of certain other phenolic compounds such as chlorogenic acid, coumaric acid, rutin, and resveratrol. So whilst bilberry wins on anthocyanins, blueberries have their own nutritional strengths.

Availability: Bilberries are primarily found in Europe and are sold fresh, frozen, dried, or as preserves. In North America and Australia, you’re more likely to encounter bilberry as a supplement extract rather than a fresh fruit.

What are the proven benefits of bilberry?

1. Rich antioxidant activity

The high anthocyanin content makes bilberry one of the more potent natural antioxidant sources. Studies confirm that bilberry extracts demonstrate strong antioxidant activity in laboratory settings, with the capacity to neutralise free radicals and reduce oxidative stress markers 1.

Flavonoids like anthocyanins belong to a large family of naturally occurring phenolic compounds found throughout the plant kingdom. Beyond their role in human health, these compounds help protect plants from bacterial and fungal infections, ultraviolet radiation, and physical damage.

My take: The antioxidant activity is well-established in laboratory studies. Whether this translates to meaningful clinical benefits is another question—antioxidants have generally disappointed in large-scale human trials for preventing chronic diseases. Still, getting antioxidants from whole foods (or food-derived supplements) is likely preferable to isolated compounds.

2. May help slow myopia progression

Myopia affects roughly 23% of the world’s population—about 1.4 billion people—with rates exceeding 90% among schoolchildren in some East Asian countries. High myopia increases the risk of serious complications including retinal detachment, glaucoma, and macular degeneration.

One randomised controlled trial followed 64 children with high myopia over two years. Half received capsules containing bilberry extract plus vitamin E, whilst the other half received no treatment. The group taking the bilberry formula showed improvements in refractive error and axial length measurements in the right eye, and these differences persisted even after discontinuing the supplement 3.

Worth noting: This is a single small study, and the lack of a proper placebo control (the comparison group received nothing rather than an inactive pill) weakens the findings. I wouldn’t recommend bilberry as a primary strategy for myopia control, but it’s an interesting area worth watching.

3. Reduces eye fatigue from screen use

Anyone who spends hours staring at a computer or phone screen knows the feeling of tired, strained eyes. This collection of symptoms—sometimes called computer vision syndrome—can include itchy or burning eyes, headaches, blurred vision, and general eye discomfort.

A prospective, randomised, double-blind, placebo-controlled study examined 281 office workers who took either bilberry extract (480 mg daily) or placebo for eight weeks. Those taking bilberry showed improvements in visual fatigue measurements as well as subjective symptoms like eye pain, heaviness, and discomfort 4.

My take: This is actually one of the better-designed bilberry studies, with a proper placebo control and reasonable sample size. The effect sizes were modest but measurable. If you spend long hours at a screen and struggle with eye fatigue, this might be worth trying—though taking regular breaks, adjusting screen brightness, and ensuring proper lighting are probably more important first steps.

4. May improve dry eye symptoms

Dry eye disease affects anywhere from 20% to 50% of the population, depending on how it’s defined and measured. The condition can significantly impact quality of life, making everyday activities like reading, driving, and watching television uncomfortable.

A small randomised, double-blind, placebo-controlled study of 22 healthy subjects with dry eye symptoms found that oral standardised bilberry extract increased tear production over four weeks, particularly in those with more severe symptoms 5.

The catch: Twenty-two participants is really quite small for drawing firm conclusions. The results are encouraging but hardly definitive. If you’re dealing with dry eyes, evidence-based treatments like artificial tears, omega-3 fatty acids, and addressing underlying causes should take priority.

5. May support blood sugar regulation

Diabetes management typically relies on diet, exercise, and medication. Some researchers have investigated whether bilberry might offer additional support for blood sugar control.

A small randomised, double-blind controlled trial in eight participants with type 2 diabetes (managed through diet and lifestyle alone) found that bilberry capsules reduced the glucose and insulin response after a glucose tolerance test compared to placebo 6.

Reality check: Eight participants. That’s not a typo—just eight people. This is hypothesis-generating research at best. There’s theoretical plausibility based on anthocyanins’ effects on glucose metabolism 7, but anyone with diabetes should focus on proven interventions and speak with their doctor before adding supplements. See also our article on diabetic bladder dysfunction for information about how diabetes affects urinary health.

6. Does NOT improve normal night vision

Here’s where I have to burst a popular bubble. The romantic story of RAF pilots eating bilberry jam to improve their night vision during World War II has been thoroughly investigated—and the evidence simply isn’t there.

A systematic review of 12 placebo-controlled trials found no rigorous demonstration that bilberry improves or enhances night vision in people who already have normal vision 8. The review also noted a complete lack of rigorous research supporting bilberry for night vision problems caused by eye diseases.

In practice: If you’re buying bilberry supplements hoping for better night vision, save your money. This appears to be a persistent myth, possibly military propaganda from the war (the RAF may have wanted to conceal their use of radar from the Germans). Marketing hasn’t caught up with the science.

7. May modulate inflammatory markers

Inflammation is the body’s normal response to infection or injury, but chronic low-grade inflammation is linked to various health problems. Some researchers have investigated whether bilberry affects inflammatory markers.

A small human randomised controlled trial found that bilberry juice modulated several inflammation-related markers including C-reactive protein, interleukins IL-6 and IL-15, and tumour necrosis factor (TNF-alpha). These changes could theoretically help regulate the NF-kappaB inflammatory pathway 9.

My assessment: Interesting mechanistic findings, but translating laboratory markers into real-world health outcomes is tricky. I wouldn’t take bilberry specifically to reduce inflammation—there are better-evidenced approaches including diet modification, exercise, and omega-3 fatty acids from fish oil.

8. Potential protection against macular degeneration and cataracts (animal research only)

Age-related macular degeneration and cataracts are increasingly common eye conditions, and there’s growing concern about blue light exposure from screens potentially accelerating these problems in younger people.

In an animal study, mice given bilberry extract showed antioxidant effects and protection against macular degeneration and cataracts—whilst 70% of the control group taking only vitamin E developed these conditions over three months 10.

A word of caution: Animal research often doesn’t translate to humans. This is promising but far from proof that bilberry prevents eye diseases in people. For eye health, consider proven strategies like not smoking, wearing sunglasses, and potentially lutein supplementation, which has more robust evidence.

Side effects of bilberry

For most people, eating bilberry as a food (fresh, frozen, dried, or as jam) is safe. Bilberry supplements are also generally considered safe when used at recommended doses for short periods.

Reported side effects have been relatively mild and uncommon:

Nausea and mild heartburn
Flatulence and gastrointestinal upset
Skin rash
Fatigue

The NHS and European Medicines Agency note that bilberry has been used traditionally without significant safety concerns, though large-scale safety studies are lacking 11.

Safety precautions (9 contraindications)

1. Pregnancy, breastfeeding, and children

Safety hasn’t been established for pregnant or breastfeeding women or for children. Stick to dietary amounts (normal food consumption) rather than concentrated supplements.

2. Bleeding disorders or anticoagulant use

Bilberry’s anthocyanins may have mild anticoagulant (blood-thinning) effects. Avoid bilberry supplements if you have bleeding disorders or take blood thinners including:

Aspirin
Clopidogrel (Plavix)
Warfarin (Coumadin)
Heparin, enoxaparin, or dalteparin
NSAIDs like ibuprofen, naproxen, or diclofenac

3. Diabetes medications

Bilberry may lower blood sugar. If you take diabetes medications, discuss with your doctor before using bilberry supplements—dose adjustments might be needed. Relevant medications include:

Insulin
Metformin
Glimepiride, glyburide, or glipizide
Pioglitazone or rosiglitazone

4. Upcoming surgery

Stop bilberry supplements at least two weeks before scheduled surgery due to potential effects on blood sugar control and bleeding risk.

5. Bilberry leaves

The fruit is safe; the leaves are not. Bilberry leaves contain high concentrations of tannins and have been associated with weight loss, muscle spasms, and potentially serious toxicity with prolonged use. Only consume the berries.

6. Herbs that affect blood sugar

Avoid combining bilberry with other supplements that lower blood sugar, such as devil’s claw, fenugreek, garlic, guar gum, Panax ginseng, psyllium, and Siberian ginseng.

7. Herbs that affect blood clotting

Avoid combining bilberry with supplements that may affect clotting, including angelica, capsaicin, clove, danshen, ginger, ginkgo, and turmeric.

8. Chromium supplements

Chromium may also affect blood sugar, so combining it with bilberry could theoretically increase hypoglycaemia risk.

9. Berry allergies

Though rare, allergic reactions to berries can occur. Two documented cases involved symptoms including itching, shortness of breath, and anaphylactic shock. Berries may contain sulfites, vasoactive amines, benzoates, or salicylates that can trigger reactions in sensitive individuals.

Dosage information

Research has used widely varying doses, making it difficult to recommend an optimal amount. Based on clinical trials (typically lasting 8 to 12 weeks), here are the ranges that have been studied:

Eye conditions: 59 to 480 mg of bilberry extract daily
Blood sugar support: 50 to 300 grams of whole berries per meal
Cholesterol: 65 to 300 grams of berries, or 320 mg of extract daily
Chronic venous insufficiency: approximately 173 mg of anthocyanins daily

Most commercial supplements provide between 80 and 160 mg of standardised extract per capsule, typically standardised to contain 25% anthocyanins.

As with any supplement, discuss with a healthcare professional before starting—particularly if you have any of the conditions listed in the contraindications above.

The bottom line

Bilberry is a traditional European berry with genuinely high anthocyanin content and documented antioxidant properties. The evidence for specific health benefits is mixed: there’s reasonable support for reducing eye fatigue from screens, modest evidence for dry eye symptoms, and interesting but preliminary findings for blood sugar effects and inflammation.

The night vision claims, however, don’t hold up. And the animal research on macular degeneration, whilst intriguing, needs human confirmation.

For most people, bilberry supplements are probably safe for short-term use, but those taking blood thinners, diabetes medications, or facing surgery should steer clear. If you’re interested in eye health specifically, lutein and astaxanthin have more extensive research behind them and might be worth considering alongside or instead of bilberry.