Cranberry in various forms has been used by women for decades to help treat Urinary Tract Infections (UTIs). Up to 27% of women report using cranberry to help treat a UTI (1). But does it actually work? Primary Care post-doctoral researcher, Dr Oghenekome Gbinigie, explains findings from her recent studies.

close up of lots of cranberries © Pixabay

Cranberry contains sugars called proanthocyanidins (PAC for short). The PAC found in cranberry is unique and is believed to block E.coli (the bug that commonly causes UTIs) from binding to the lining of the bladder (2). This could, in theory, prevent a UTI from being caused and sustained.

Hard to swallow?

Multiple studies have tested cranberry extract as a way of preventing UTIs. The findings of these studies have been mixed, with a number of promising results (3). However, the methods used by many of these studies have been flawed (4); some have not specified the amount of PAC (thought to be the active ingredient in cranberry) in the intervention that they used, and other studies have had very high drop-out rates (sometimes over half of the participants) due to participants struggling to drink large amounts of cranberry juice over long periods.

So, this has been tested before? 

We conducted a systematic review (that is, a comprehensive review of the evidence on a particular topic) to determine whether there was evidence for using cranberry extract to treat an acute (current) UTI. We found that very few studies had tested cranberry extract as an acute UTI treatment, thus at present, there is insufficient evidence for or against this practice (5).

A wee bit of evidence…

We decided to run a small-scale study (known as a feasibility trial) testing cranberry capsules as an acute UTI treatment in women presenting to their GP practices with urinary symptoms. The main aim of this feasibility trial was to test whether the study design worked and was liked by participants (called a ‘feasibility’ study). (6)

Women in the study were randomly assigned to one of three groups:

Group 1 - Usual treatment with immediate antibiotics 

Group 2 - Treatment with immediate antibiotics AND immediate cranberry capsules. 

Group 3 - Initial treatment with cranberry capsules. Women in this group were also given an antibiotic prescription that they could take to the chemist at a later date if they didn’t get better with cranberry capsules alone (‘back-up antibiotics’). 

We were able to recruit one beyond our target (46 women) and faster than we anticipated (9 women/month on average (7). There was a preliminary suggestion that women in groups 2 and 3 took fewer antibiotics than women in group 1. Furthermore, certain measures of symptom control were better in women in group 2 compared with women in group 1.

You can watch a short video explaining the results of the feasibility trial here. 

More juicy details

We interviewed women who had experienced a recent UTI to get their thoughts on using non-antibiotic options, like cranberry extract, to manage acute UTIs (8). Women often felt that antibiotics were a reliable and effective treatment, but they were also keen to avoid them if they could due to concerns about becoming ‘immune’ to their effects. Many women were open to trying non-antibiotic treatments first in certain situations, such as with milder symptoms, earlier symptoms, and when they had no important upcoming engagements.

A very berry future?

If cranberry extract is found to be an effective treatment for acute UTIs, then it could be offered to women as an initial treatment, with antibiotics offered as a backup treatment. This could, in turn, significantly reduce antibiotic consumption for this common condition. My hope is that a large-scale, well-conducted trial of cranberry will be conducted, providing definitive evidence of the safety and effectiveness of cranberry extract as an acute UTI treatment.

About the author:

Dr Oghenekome Gbinigie; MA (Cantab), MB BChir, MRCGP, DRCOG, DfSRH, PG Cert (Health Research), DPhil (Oxon). Academic GP, Nuffield Department for Primary Care Health Sciences, University of Oxford.

References

1. Ref: Butler CC, Hawking MK, Quigley A, McNulty CA. Incidence, severity, help-seeking, and management of uncomplicated urinary tract infection: a population-based survey. Br J Gen Pract. 2015;65(639):e702-e7]. 

2. [Ref: Howell AB, Vorsa N, Marderosian AD, Foo LY. Inhibition of the adherence of P-fimbriated Escherichia coli to uroepithelial-cell surfaces by proanthocyanidin extracts from cranberries. New England Journal of Medicine. 1998;339(15):1085-6].

3. [Refs: Fu Z, Liska D, Talan D, Chung M. Cranberry reduces the risk of urinary tract infection recurrence in otherwise healthy women: a systematic review and meta-analysis. The Journal of nutrition. 2017;147(12):2282-8 AND Luís Â, Domingues F, Pereira L. Can cranberries contribute to reducing the incidence of urinary tract infections? A systematic review with meta-analysis and trial sequential analysis of clinical trials. The Journal of urology. 2017;198(3):614-21]. 

4.  [Ref: Jepson RG, Williams G, Craig JC. Cranberries for preventing urinary tract infections. The Cochrane Library. 2012.

5. [Ref: Gbinigie OA, Spencer EA, Heneghan CJ, Lee JJ, Butler CC. Cranberry Extract for Symptoms of acute, Uncomplicated Urinary Tract Infection: A Systematic Review. Antibiotics. 2021;10(1):12].

6. [Ref: Gbinigie O, Allen J, Boylan A-M, Hay A, Heneghan C, Moore M, et al. Does cranberry extract reduce antibiotic use for symptoms of acute uncomplicated urinary tract infections (CUTI)? Protocol for a feasibility study. Trials. 2019;20(1):1-9] 

7. [Ref: Gbinigie O, Allen J, Williams N, Moore M, Hay AD, Heneghan C, et al. Does cranberry extract reduce antibiotic use for symptoms of acute uncomplicated urinary tract infections (CUTI)? A feasibility randomised trial. BMJ Open. 2021;11(2):e046791]. 

8. [Ref: Gbinigie, O.A., Tonkin-Crine, S., Butler, C.C., Heneghan, C.J. and Boylan, A.M., 2022. Non-antibiotic treatment of acute urinary tract infection in primary care: a qualitative study. British Journal of General Practice72(717), pp.e252-e260].