Encyclopedia/Botanical/Folk medicine/encyclopedia-cranberry

Cranberry

Vaccinium macrocarpon

Sources

5 listed

Best forAnyone interested in the research on urinary tract support, especially women with a pattern of recurrent urinary tract infections, as a traditional food and supplement alongside medical care.

Clinical evidence

Clinical

SafetyUse with cautionCranberries are usually well tolerated as food. Medicinal preparations require attention to interactions with warfarin and tacrolimus, kidney disorders and a history of urinary stones. Gastrointestinal complaints and skin reactions can occur. New urinary symptoms require assessment; cranberry does not replace necessary treatment.

Tradition

Folk medicine

Common preparations

Fresh JuiceCapsuleDried FruitsSyrupMixed Juice

In short

Summary of findings for quick reference

Cranberry is native to North America and has an Indigenous food tradition. European botanical descriptions and later ethnographic publications do not date the beginning of that tradition. Waugh names two cranberry species together as food fruits in 1916. King’s American Dispensatory (1898) describes large cranberry as a skin poultice, whereas today’s urinary-tract use rests on more recent observations and studies. Food use, historical skin use and modern urinary research should therefore be considered separately.

The 2023 Cochrane review by Williams and colleagues combined 50 studies with 8857 participants. It found a preventive benefit in women with recurrent UTIs, children and people at increased risk after certain interventions. Little or no benefit was found in elderly institutionalised people, certain bladder-emptying disorders, or pregnancy. Laboratory inhibition of bacterial adhesion suggests a possible mechanism, not proof of treatment for an existing infection.

EMA describes traditional use of a specific expressed cranberry juice for prevention and relief of mild recurrent lower urinary tract symptoms in adult women after medical assessment. This is neither blanket approval of cranberry products nor a food health claim. Seek medical advice for new symptoms, fever, blood in urine or worsening symptoms. Cranberry does not replace antibiotic treatment when required. Cranberry preparations should not be used with warfarin or tacrolimus.

Clinical evidence ↔ Historical significance

We display two separate evidence categories: clinical evidence from modern trials and historical significance from documented healing tradition. Both are valuable, but they answer different questions.

In every encyclopedia entry we evaluate two distinct categories of evidence. Clinical evidence as used in trials meets a narrower but scientifically essential bar. At the same time, the hundreds of thousands of plant species worldwide have only partially been captured and tested in modern studies.

Alongside the trial picture our researchers compile a comprehensive overview of where and since when a plant has been used across different traditions of natural medicine. When a plant has been used as a medicinal plant in many cultures across many generations, that historical significance deserves to be visible too.

Our position: a truly informative overview emerges only when both categories sit side by side. We communicate transparently what counts as what.

Overview

Cranberry (Vaccinium macrocarpon) is a low evergreen shrub in the heath family (Ericaceae), native to eastern and north-central North America and cultivated for its red, tart berries. Products include fresh or dried berries, juices, and powders or extracts in capsules. Lingonberry (Vaccinium vitis-idaea), familiar in Austria, is a different species in the same genus. Cranberry products are widely imported; Kew also records the plant as introduced in Austria.

Investigated constituents include proanthocyanidins with A-type linkages, which can inhibit adhesion of certain E. coli bacteria in laboratory experiments. Clinical research mainly concerns UTI prevention. An EMA monograph published in 2023 also describes traditional use of a specific expressed cranberry juice for prevention and relief of mild recurrent lower urinary tract symptoms in adult women after serious causes have been excluded by a doctor. This medicinal classification differs from food health claims and from proof of effective treatment of acute infections.

History

Cranberries belong to the food traditions of Indigenous communities in northeastern North America. Waugh listed Vaccinium macrocarpon together with Vaccinium oxycoccos among food fruits in 1916. The same chapter describes drying and storing berries generally, without assigning those methods exclusively to large cranberry. King’s American Dispensatory (1898) also records domestic use of Vaccinium macrocarpon as a poultice for inflammatory swellings. This is a historical skin-use record, not a present-day recommendation. Commercial cultivation developed in the nineteenth century in areas including Cape Cod and Wisconsin.

Modern urinary-tract research developed during the twentieth century. Moen published a clinical observation report in 1962; Sobota investigated inhibition of bacterial adhesion by cranberry juice in 1984. Foo and colleagues characterised relevant proanthocyanidins in 2000. Cochrane assessments changed as the study base grew: the 2012 review found no clear preventive benefit, whereas the larger 2023 review found benefit in specified groups. Food-use history should be distinguished from this newer research and from medicinal and food-claim assessments.

Mechanism

Proanthocyanidins with A-type linkages are among the cranberry tannins investigated. Certain isolated fractions inhibited adhesion of uropathogenic E. coli strains to cell surfaces in the laboratory. These bacteria use fine surface structures called fimbriae for attachment. This anti-adhesion effect is a possible explanation for preventive use. These experiments alone do not establish which compounds reach the urinary tract at effective concentrations after consumption.

Cranberries also contain organic acids, including quinic, malic and citric acids, anthocyanins that contribute to their red colour, and vitamin C. Composition, dose and preparation matter for clinical assessment. A laboratory finding for an isolated constituent group cannot be transferred to every juice or capsule. EFSA also judged the mechanistic evidence submitted for Pacran limited in 2025.

The 2023 Cochrane review by Williams and colleagues includes 50 studies and 8857 participants. It found a preventive benefit in women with recurrent UTIs, children and people at increased risk following certain interventions. In women with recurrent UTIs, eight studies involving 1555 participants yielded a risk ratio of 0.74 versus placebo or no specific treatment. Little or no benefit was found in elderly institutionalised people, pregnant women, or adults with certain bladder-emptying disorders. Products, doses and measured outcomes varied considerably.

EFSA evaluates food health claims using the data submitted for each application. Its 2025 assessment of Pacran also found the evidence insufficient for the proposed lower urinary tract effect. This does not automatically contradict pooled findings for different cranberry products in the Cochrane review. Traditional medicinal use of expressed juice in the EMA monograph is another distinct assessment. None establishes a universal dose for juices, powders and extracts. The often cited 36 mg PAC amount is not a proven standard dose for every product.

Evidence

4 Outcomes evaluated. Sorted by grade.

Outcome	Class	Grade	Effect	Studies	Refs
Recurrent urinary tract infections (women)Women with a pattern of recurrent UTIs	Clinical	B	Modest Improvement	8 studies	[1]
Acute urinary tract infection (treatment)Adults with acute UTI	Insufficient	I	No proven acute treatment		[2][4]
Anti-adhesion mechanism (uropathogenic E. coli, in vitro)Laboratory studies on bacterial adhesion	Traditional	I	In Vitro Signal		[3]
General urinary tract infection prevention (mixed populations)Children, people at increased risk after interventions, care-home residents, pregnant women and people with bladder-emptying disorders	Clinical	C	Mixed Effect		[1]

Usage

Forms and preparation

Check the label of cranberry juice for cranberry content, added sugar and whether it is juice, concentrate or a mixed drink. These products are not interchangeable. Unsweetened juice is very tart and can be diluted with water to taste. Dried cranberries are also often sweetened. The label cranberry juice alone does not establish a particular dose. Distinguish whole-fruit powders from extracts in capsules. The milligram amount alone says little about proanthocyanidin (PAC) content, and the analytical method affects the reported PAC value. Follow the specific product instructions and seek advice for recurrent symptoms. As food, fresh or frozen berries can be cooked with water and sugar to taste into a compote. Such a serving is not a medicinal dose.

Dosage

No uniform dose is established for all cranberry products. For a precisely defined expressed juice from fresh fruit (DER 1:0.6 to 0.9), the EMA monograph specifies 30 ml daily for traditional prevention and 50 to 60 ml two to four times daily for traditional relief of mild recurrent symptoms. Both apply to adult women after a doctor has excluded serious causes. These doses cannot be transferred to arbitrary juices, concentrates, powders or capsules; follow the medicine leaflet. Seek medical advice if UTI symptoms develop during preventive use. For symptom relief, reassessment is needed if symptoms persist beyond four days, or sooner for worsening symptoms, fever, blood in urine or spasmodic pain. Cranberry does not replace antibiotic treatment when required. Medicinal use is not recommended in men, under 18, or during pregnancy and breastfeeding. Avoid cranberry preparations with warfarin or tacrolimus.

Safety

Safety profile

Seek medical advice for new urinary symptoms, fever, blood in urine or worsening symptoms. A bladder infection can spread to the kidneys. Cranberry does not replace antibiotic treatment when required. Traditional medicinal use of the expressed juice in adult women requires prior exclusion of serious causes by a doctor. This use is not recommended in men, under 18, or during pregnancy or breastfeeding. Kidney disorders require medical supervision. Avoid cranberry preparations with warfarin or tacrolimus. Cranberry may increase warfarin effects; decreased tacrolimus blood levels have been reported. With a history of urinary stones, seek medical advice because concentrated preparations contain oxalate. Reported adverse effects include nausea, diarrhoea, dyspepsia, hives and rash. Medicinal use is contraindicated with cranberry allergy. Also check juices and dried fruit for added sugar.

Look-alikes

Botany

Family

Ericaceae

Native regions

North America (native), New England and Great Lakes (commercial cultivation), Quebec and the maritime provinces of Canada, Austria (introduced)

Harvest window

September to November (commercial harvest on flooded bogs)

Habitat

Cranberry grows on acidic, peaty soils in bogs and wetlands. Its native range extends from eastern Canada to the north-central and eastern USA. Commercial beds are flooded temporarily for harvest or winter protection; the plants do not grow permanently in water. Kew also records the species as introduced in Austria. Native relatives there include lingonberry (Vaccinium vitis-idaea) and small cranberry (Vaccinium oxycoccos).

Identification & foraging

A low, creeping evergreen shrub with slender wiry stems and small narrow leathery leaves. The pink flowers have reflexed petals. Berries are oval to round, bright red when fully ripe, larger than Vaccinium oxycoccos, and very tart raw. The plant grows close to the ground in the wild; commercial cultivation uses bogs that can be flooded for harvest.

Similar plants and look-alikes

Unpleasant

Lingonberry (Vaccinium vitis-idaea)

Lingonberry (Vaccinium vitis-idaea) is a related species with smaller berries and its own flavour. In Austria it is significantly more traditional than the American cranberry. Lingonberry grows wild in mountain forests, heaths and bogs. Its berries are smaller, firmer, slightly more bitter, and traditionally served as a compote alongside game. Botanically both belong to the genus Vaccinium. The research on UTI prevention has focused on the American cranberry (V. macrocarpon).

Read the entry: Lingonberry

Unpleasant

Small cranberry (Vaccinium oxycoccos)

The small cranberry (Vaccinium oxycoccos) is a smaller European cranberry species that grows in the raised bogs of Central and Northern Europe. Its growth habit is very similar to the American cranberry, but its berries are noticeably smaller. It has a culinary and folk tradition in Central Europe but is far less studied in the international research base on urinary tract support than V. macrocarpon. Occasional finds are possible in Austrian raised-bog landscapes.

FAQs

What is the difference between cranberry and Preiselbeere?

Cranberry (Vaccinium macrocarpon) is the American large-fruited species, native to north-eastern North America and commercially cultivated for juice and capsules. Preiselbeere (Vaccinium vitis-idaea, lingonberry) is a smaller European relative that grows wild in mountain forests, heaths and bogs across Austria and northern Europe. Both belong to the heath family (Ericaceae) and share related polyphenol chemistry, including proanthocyanidins. In Austria the Preiselbeere is the more traditional reference, often served as a tart compote alongside game and savoury dishes. Cranberry products are now marketed as juices and supplements, among other forms. The research base on urinary tract support is mostly built on Vaccinium macrocarpon.

I think I have an acute bladder infection. Can I just take cranberry?

No. Have new symptoms medically assessed, especially with fever, blood in urine or worsening symptoms. Cranberry does not replace antibiotic treatment when required; a bladder infection can spread to the kidneys. Most clinical trials concern prevention. EMA does describe traditional symptom relief with a specific expressed juice for mild recurrent symptoms in adult women, but only after serious causes have been excluded by a doctor. This is not a recommendation to self-treat a suspected acute infection with cranberry.

Does cranberry interact with warfarin?

Cranberry products may increase the effect of warfarin and the risk of bleeding. EMA and the UK NHS therefore advise avoiding the combination. This is not limited to daily capsules or juice; a blanket reassurance for occasional consumption is unwarranted. Discuss cranberry with your treating team and do not change your warfarin dose yourself. Cranberry preparations should also be avoided with tacrolimus.

Juice or capsule, what is the better form?

No universally better form is established. The Cochrane review could not determine whether juice or tablets are more effective. Capsules may be more convenient; juices vary in fruit, sugar and PAC content. Whole-fruit powders and extracts in capsules are also not equivalent. The particular preparation, composition and studied use matter. EMA doses for a defined expressed juice do not automatically apply to supermarket juice or capsules.

References

5 sources.

Gabrielle Williams; Christopher I Stothart; Deirdre Hahn; Jacqueline H Stephens; Jonathan C Craig; Elisabeth M Hodson. Cranberries for preventing urinary tract infections. 2023. doi:10.1002/14651858.CD001321.pub7
Ruth G Jepson; Lara Mihaljevic; Jonathan C Craig. Cranberries for treating urinary tract infections. 2023. doi:10.1002/14651858.CD001322.pub2
L Y Foo; Y Lu; A B Howell; N Vorsa. The structure of cranberry proanthocyanidins which inhibit adherence of uropathogenic P-fimbriated Escherichia coli in vitro. 2000. doi:10.1016/s0031-9422(99)00573-7
European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). European Union herbal monograph on Vaccinium macrocarpon Aiton, fructus. 2022. Source
EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA). Pacran®, a powder obtained from cranberries, and defence against bacterial pathogens in the lower urinary tract: Evaluation of a health claim pursuant to Article 13 (5) of Regulation (EC) No 1924/2006. 2025. doi:10.2903/j.efsa.2025.9319

Legal notice: The depiction of historical significance and traditional use is context within our encyclopedia and not a health claim for any product, not a treatment promise, and not a substitute for medical advice. What may be stated on product labels, product pages, or in advertising is governed by the applicable legal requirements.