Bilberry Sources & Extracts
Almost everything that makes bilberry worth studying — the eye, vascular, and metabolic effects on the other three pages — comes down to its anthocyanins, and almost every practical mistake people make with bilberry comes down to not understanding those pigments. A wild European bilberry is not a supermarket blueberry; a "36% anthocyanoside" extract is not the same as a scoop of berry powder; and even the best extract is limited by the fact that anthocyanins are absorbed poorly and broken down quickly. This page covers how bilberry differs from cultivated blueberry, what the standardisation numbers on a supplement label actually mean, how much the trials used, why bioavailability is the quiet ceiling on every result, and what a label does and does not reveal about pigment content.
Table of Contents
- Bilberry Is Not a Blueberry
- What the Anthocyanins Actually Are
- Fresh, Frozen, Dried, Juice, Powder: How Form Changes the Pigment
- Standardised Extracts and the 25% / 36% Numbers
- Dosing: How Much, How Often
- Bioavailability: the Quiet Limiting Factor
- What a Supplement Label Does and Does Not Show
- Cooking and Eating Bilberries
- Quality, Cautions & Safety
- Key Research Papers
- External Authoritative Resources
- Connections
- Featured Videos
Bilberry Is Not a Blueberry
The single most useful fact about bilberry sources is that "bilberry" and "blueberry" are different plants that behave differently. Bilberry is Vaccinium myrtillus, a small wild shrub of northern European and Asian heath and forest; the familiar cultivated blueberry of North American supermarkets is mostly highbush blueberry, Vaccinium corymbosum. They are cousins in the same genus, but three practical differences matter:
- Pigment location. This is the big one. In a bilberry the anthocyanin pigment saturates the whole fruit, so the flesh and juice are deep purple; in a typical highbush blueberry the anthocyanins sit mainly in the skin and the flesh is pale green-white. Crush each and the difference is obvious on the fingers. Because bilberry pigments the pulp too, it packs substantially more anthocyanin per gram.
- Wild vs cultivated. Bilberry is essentially still a wild-harvested fruit — it resists commercial cultivation — while blueberries are a large cultivated crop. Wild harvest means more batch-to-batch variation in anthocyanin content, driven by species, region, altitude, sun exposure, and season.
- Anthocyanin profile. The two fruits carry overlapping but distinct mixtures of individual anthocyanins, which is why analytical papers can tell them apart and why substituting one for the other is not chemically neutral.
Müller, Schantz, and Richling (2012) quantified exactly this with HPLC, comparing the anthocyanin content of bilberries, blueberries, and their juices, and found up to 1,017 mg of anthocyanins per 100 g fresh weight in bilberries against up to 438 mg in blueberries; commercial bilberry juices were also far richer in anthocyanins than blueberry juices. Burdulis and colleagues (2009) compared the two fruits' anthocyanin composition and found different dominant pigments — cyanidin in bilberry, malvidin in blueberry (in their analysis of skins, the highest total anthocyanin values were in blueberry cultivars). Bilberry's higher whole-fruit pigment load is part of why bilberry, not blueberry, is the traditional medicinal berry. That higher pigment load is what distinguishes "bilberry" products — so whether a product actually contains Vaccinium myrtillus matters to what it delivers.
What the Anthocyanins Actually Are
Bilberry's anthocyanins are a family of about fifteen related pigments. Chemically they are glycosides — sugar-attached forms — of five anthocyanidin "backbones": delphinidin, cyanidin, petunidin, peonidin, and malvidin. Each backbone appears attached to different sugars (glucose, galactose, arabinose), which is how you arrive at roughly fifteen distinct anthocyanins. In bilberry, delphinidin and cyanidin glycosides dominate, and delphinidin’s abundance is part of what gives bilberry its especially dark, blue-leaning colour.
Two vocabulary points clear up most label confusion:
- Anthocyanin = the sugar-attached (glycoside) pigment as it exists in the fruit. Anthocyanoside is an older, largely synonymous term used in the European literature.
- Anthocyanidin = the sugar-free core (aglycone) left after the sugar is removed. Because the sugar makes up a big fraction of the molecule’s weight, the same extract is a higher percentage when expressed as anthocyanosides and a lower percentage when expressed as anthocyanidins. That is the whole reason the same standardised bilberry extract is described both as "36% anthocyanosides" and as "25% anthocyanidins" — two ways of measuring the same material.
Lätti, Riihinen, and Kainulainen (2008) analysed 179 wild Vaccinium myrtillus plants from 20 populations along a roughly 1,000 km south–north axis in Finland, identified 15 anthocyanins, and found extensive variation within and between populations (lower totals in the south; delphinidin glycosides dominating in northern berries, cyanidin glycosides in southern ones) — a reminder that "bilberry" is not one fixed dose of pigment but a range, which is precisely why standardised extracts exist. For the pure-compound view of these pigments, see the dedicated Anthocyanins page.
Fresh, Frozen, Dried, Juice, Powder: How Form Changes the Pigment
Anthocyanins are chemically fragile — sensitive to heat, oxygen, light, and changes in acidity — so the form you buy affects how much intact pigment you actually consume.
- Fresh bilberries — the reference standard, but genuinely fresh wild bilberries are seasonal and regional, hard to find outside northern Europe.
- Frozen — an excellent practical choice; freezing preserves anthocyanins well, and frozen wild bilberries retain most of their pigment.
- Dried — convenient and concentrated by weight, but drying (especially with heat) degrades some anthocyanin; quality varies widely.
- Juice — can be anthocyanin-rich but is sensitive to processing and storage; Müller and colleagues (2012) analysed commercial juices and found bilberry juices ranging from 1,610 to 5,963 mg anthocyanins per litre, far above the blueberry juice tested (417 mg/L).
- Powder — freeze-dried whole-fruit powder can retain pigment well; spray-dried or heat-processed powders may lose more. Powder is not the same as a standardised extract.
- Standardised extract (capsule/tablet) — the concentrated, quantified form used in most clinical trials, covered next.
In summary: among foods, frozen wild bilberries retain pigment most reliably year-round; the doses used in trials were delivered as standardised extracts, which contain a known amount of anthocyanin.
Standardised Extracts and the 25% / 36% Numbers
Because wild bilberry pigment content varies so much, the pharmaceutical answer is a standardised extract: the fruit is extracted and the product is adjusted so that every batch contains a defined percentage of anthocyanins. The best-known standard, established by a standardized Italian bilberry extract and adopted across much of the research, is an extract standardised to 36% anthocyanosides, equivalent to about 25% anthocyanidins — the same material expressed two ways, as explained above. A well-defined standardised extract also fixes the profile of the fifteen anthocyanins, not just the total, so that it matches the natural fruit rather than being spiked with cheaper single pigments.
This standardisation is why the clinical literature is even interpretable. When Hoggard and colleagues (2013) studied a bilberry extract standardised to 36% (w/w) anthocyanins for glycemic response, or Riva and colleagues (2017) used a standardised bilberry extract for dry eye, the reader knows roughly what material was delivered. An unstandardised "bilberry" capsule offers no such guarantee. On a product label, a stated standardisation (for example, "standardised to 25% anthocyanidins" or "36% anthocyanosides") is the only figure that indicates how much anthocyanin is present.
Dosing: How Much, How Often
There is no official Recommended Dietary Allowance for bilberry or for anthocyanins — they are not essential nutrients — so "dose" means the amounts that have been used in studies and in traditional European practice, not a requirement.
- Standardised extract (25% anthocyanidin / 36% anthocyanoside): amounts in the range of 80–160 mg up to three times daily are commonly cited in herbal references; the studies themselves used different amounts for different endpoints. Vaneková and Rollinger (2022), reviewing the clinical research, found contradictory results with no clear conclusion as to benefits or dosages.
- Eye-fatigue and dry-eye trials used standardised extracts over periods of weeks (the Riva dry-eye trial ran 4 weeks in 22 enrolled adults); the metabolic (glycemic) study by Hoggard gave 8 men with diet-controlled type 2 diabetes a single 0.47 g capsule — which the authors equate to about 50 g of fresh bilberries — before a carbohydrate drink.
- Whole fruit: the whole-diet studies used berries eaten as food, fresh or frozen, a form with a long record of safe use as food.
Because anthocyanins clear the body quickly (next section), researchers describe split dosing through the day as more physiologic than a single large dose. The trials ran over several weeks, and their results are summarised, with their limits, on the Eye & Vision, Circulation & Veins, and Blood Sugar pages. Decisions about supplements belong with a clinician.
Bioavailability: the Quiet Limiting Factor
Here is the fact that quietly governs every bilberry result: anthocyanins are absorbed poorly. Human bioavailability studies consistently find that only a small percentage of ingested anthocyanin appears intact in the blood, that plasma levels peak low and fall within a few hours, and that much of the pigment is metabolised in the gut and liver into other phenolic compounds or handled by the gut microbiota before it ever reaches tissue.
Mazza, Kay, Cottrell, and Holub (2002) gave freeze-dried blueberry powder with a high-fat meal and detected 19 of its 25 anthocyanins in the blood, showing that anthocyanins can be absorbed intact, in their sugar-attached forms. Manach and colleagues (2005), in a landmark review of ninety-seven human bioavailability studies of polyphenols in the American Journal of Clinical Nutrition, placed anthocyanins among the least well-absorbed of all dietary polyphenols. In a bilberry-specific human study, Mueller and colleagues (2017) observed low anthocyanin levels in plasma and urine, with more breakdown products than intact anthocyanins reaching the circulation, and found that people with an intact colon absorbed substantially more than people without one. Kay and colleagues (2017) argue in a review that once the colonic microbial breakdown products are counted, anthocyanins are much more bioavailable than previously thought.
Two honest implications follow. First, low bioavailability is a real reason to be modest about bilberry's effects — it is part of why the clinical results are gentle rather than dramatic. Second, it reframes the mechanism: because so little intact pigment circulates, some of bilberry's benefit may come from its metabolites and from effects in the gut itself rather than from high anthocyanin concentrations in distant tissues. It is also the basis for the view that regular intake matters more than occasional megadoses, and for modest expectations. A brightly coloured berry does not deliver its colour to the bloodstream in proportion to how much is eaten.
What a Supplement Label Does and Does Not Show
In bilberry supplements, the pigment a label implies and the pigment a product contains can diverge widely. The label details that analyses and quality reviews point to:
- Species named. Genuine products list Vaccinium myrtillus. A label that says only "bilberry" with no Latin name, or names a different Vaccinium species, gives no assurance of the species — some products substitute cheaper blueberry or other berry material.
- Standardisation stated. The trial extracts were described as "standardised to 25% anthocyanidins" or "36% anthocyanosides." A milligram figure with no standardisation tells you the weight of powder, not the amount of active pigment.
- Fruit, not leaf. The research on this page concerns the fruit/berry extract. Bilberry leaf is a different product with safety concerns at high doses (see below).
- Third-party testing. Because bilberry is wild-harvested and expensive, adulteration is a documented problem. Penman and colleagues (2006) found an extract that met its claimed 25% anthocyanin content by a simple spectrophotometric assay but contained only 9% by HPLC, with the synthetic dye amaranth as the adulterant; Gaspar and colleagues (2021) rated 45% of the bilberry supplements they tested as of unacceptable quality, including bilberry-free products and products falsified with anthocyanins from other sources. Third-party testing is one way products are independently checked.
- "Proprietary blends." When bilberry is part of a blend without its own quantity and standardisation, the label does not reveal how much bilberry or anthocyanin it contains.
Bilberry sits alongside other standardised flavonoid extracts — Grape Seed Extract, French maritime pine bark extract, Rutin, and Hesperidin — and the same label questions apply to all of them.
Cooking and Eating Bilberries
The diet studies tested bilberry as a whole fruit. Frozen wild bilberries stirred into yoghurt or oatmeal, blended into a smoothie, or eaten by the handful deliver anthocyanins in that whole-food matrix. A few points from the food-chemistry research:
- Cold beats hot. Because heat degrades anthocyanins, raw or gently used berries preserve more pigment than long cooking; a briefly cooked compote or jam retains more than a long-simmered one.
- Acidity helps colour. Anthocyanins are more stable and more vividly coloured in acidic conditions, which is part of why a squeeze of lemon brightens a berry sauce.
- Whole diet, not heroic dose. The metabolic and vascular population evidence is about a regular berry-containing pattern, not an occasional megadose. Everyday, ordinary servings are the point.
- Blueberries are a fine stand-in for general health. If wild bilberries are unavailable, blueberries and other dark berries still supply anthocyanins — just less concentrated — and carry much of the same general benefit.
Quality, Cautions & Safety
- Adulteration is the main quality risk. Genuine wild bilberry extract is costly, which creates an incentive to dilute or substitute it. Species labelling, stated standardisation, and third-party testing are the main checks against it.
- Fruit is very safe; leaf is not equivalent. Bilberry fruit and its standardised extract have an excellent safety record at usual doses. Bilberry leaf preparations are a different product, and herbal-safety references describe high or prolonged use of the leaf as a concern — the two are not interchangeable.
- Bleeding and drug interactions. Concentrated anthocyanin extracts may mildly affect platelet function and can add to the glucose- and blood-pressure-lowering effects of medication; the research raises a concern for people taking anticoagulants/antiplatelets or facing surgery, and for people treated for diabetes or hypertension, whose glucose or blood pressure readings may shift.
- Pregnancy and breastfeeding. Bilberry fruit as food is fine; concentrated extracts are not well studied, and there is no good safety data on them in pregnancy or breastfeeding.
- Not a cure. No form or dose of bilberry treats eye disease, venous disease, or diabetes on its own; the research supports it at most as a supportive food or adjunct alongside medical care.
Key Research Papers
- Müller D, Schantz M, Richling E (2012). HPLC analysis of anthocyanins in bilberries (Vaccinium myrtillus L.), blueberries (Vaccinium corymbosum L.), and corresponding juices. Journal of Food Science — PubMed PMID: 22394068
- Burdulis D et al. (2009). Comparative study of anthocyanin composition, antimicrobial and antioxidant activity in bilberry and blueberry fruits. Acta Poloniae Pharmaceutica — PubMed PMID: 19702172
- Lätti AK, Riihinen KR, Kainulainen PS (2008). Analysis of anthocyanin variation in wild populations of bilberry (Vaccinium myrtillus L.) in Finland. Journal of Agricultural and Food Chemistry — PubMed PMID: 18072741
- Lätti AK et al. (2010). Anthocyanin and flavonol variation in bog bilberries (Vaccinium uliginosum L.) in Finland. Journal of Agricultural and Food Chemistry — PubMed PMID: 20000402
- Mazza G, Kay CD, Cottrell T, Holub BJ (2002). Absorption of anthocyanins from blueberries and serum antioxidant status in human subjects. Journal of Agricultural and Food Chemistry — PubMed PMID: 12475297
- Manach C et al. (2005). Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies. American Journal of Clinical Nutrition — PubMed PMID: 15640486
- Hoggard N et al. (2013). A single supplement of a standardised bilberry extract modifies glycaemic response in individuals with type 2 diabetes. Journal of Nutritional Science — PubMed PMID: 25191571
- Riva A et al. (2017). The effect of a natural, standardized bilberry extract (Mirtoselect) in dry eye. European Review for Medical and Pharmacological Sciences — PubMed PMID: 28617532
- Ghosh A et al. (2024). Effects of Vaccinium-derived antioxidants on human health: the past, present and future. Frontiers in Molecular Biosciences — PubMed PMID: 39758282
- Yang L et al. (2017). Effects of anthocyanins on cardiometabolic health: a systematic review and meta-analysis of randomized controlled trials. Advances in Nutrition — PubMed PMID: 28916569
- Penman KG et al. (2006). Bilberry adulteration using the food dye amaranth. Journal of Agricultural and Food Chemistry — PubMed PMID: 16968108
- Gaspar DP, Lechtenberg M, Hensel A (2021). Quality assessment of bilberry fruits (Vaccinium myrtillus) and bilberry-containing dietary supplements. Journal of Agricultural and Food Chemistry — PubMed PMID: 33587635
- Mueller D et al. (2017). Human intervention study to investigate the intestinal accessibility and bioavailability of anthocyanins from bilberries. Food Chemistry — PubMed PMID: 28450007
- Kay CD et al. (2017). Anthocyanins and flavanones are more bioavailable than previously perceived: a review of recent evidence. Annual Review of Food Science and Technology — PubMed PMID: 28125348
- Vaneková Z, Rollinger JM (2022). Bilberries: curative and miraculous – a review on bioactive constituents and clinical research. Frontiers in Pharmacology — PubMed PMID: 35847049