Cranberries for preventing urinary tract infections

For years, people have used cranberry products (usually juice) to prevent urinary tract infections (UTIs). This is because it is thought that cranberries contain a substance that prevents bacteria from sticking to the walls of the bladder, and that this might prevent UTIs. But do they actually work?

What does the research tell us?

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Some early studies suggested that drinking cranberry juice could reduce recurrent UTIs. However, more recent higher quality research from 2012 found that there is no benefit in preventing UTIs compared to placebo or no treatment. This study was a review of 24 studies with 4473 participants and was carried out by the Cochrane Database of Systematic Reviews, which is a gold-standard level of research.1 Other findings were that:

  • many people in the studies stopped drinking the juice, suggesting that it may be unacceptable to consume in the long term for many people
  • cranberry-derived products (such as tablets or capsules) were also ineffective. 

There have been two further randomised trials in 2016. One found no benefit in nursing home residents.2 Another study found a meaningless benefit of preventing one UTI per 3.2 years of daily drinking of cranberry juice, and the study had significant biases like being funded by a cranberry product manufacturer.3

Are there any risks in using cranberry juice anyhow?

The risk of using cranberry juice is small but includes:

  • increased sugar and calories in your diet5
  • gastrointestinal upset, such as heartburn and diarrhoea4,5
  • theoretical risk of kidney stones (high levels of oxalates).5

Other considerations

  • No single concentration of cranberry juice, extract or supplement has been studied, so it's hard to know which product to choose.
  • If you do want to try cranberry juice to prevent UTIs, it's better to drink pure, unsweetened cranberry juice (rather than sweetened cranberry juice). However, many women complain of the taste of unsweetened cranberry juice.
  • Using cranberry products to prevent UTIs may be expensive.
  • Cranberries may interact with some medicines, such as warfarin and/or aspirin.5
  • Cranberry juice is not well tolerated long term by many people.5

Recommendation

Cranberry products (juice, tablets, or capsules) are not routinely recommended to reduce the incidence of recurrent UTI. Although it is generally safe and there are theoretical reasons for a benefit, clinical studies have not definitively shown a reduction in UTIs.4 

References

  1. Jepson RG, et al Cranberries for preventing urinary tract infections Cochrane Database of Systematic Reviews. 2012
  2. Juthani-Mehta M, Van Ness PH, Bianco L, et al. Effect of cranberry capsules on bacteriuria plus pyuria among older women in nursing homes: a randomized clinical trial JAMA. 2016;316(18):1879-1887.
  3. Maki KC, Kaspar KL, Khoo C, et al. Consumption of a cranberry juice beverage lowered the number of clinical urinary tract infection episodes in women with a recent history of urinary tract infection The American Journal of Clinical Nutrition. 2016 Jun;103(6):1434-1442.
  4. Recurrent simple cystitis in women UpToDate, 2019
  5. Martini N. Cranberry products J Prim Health Care. 2014;6(2):161.

Reviewed by

Jeremy Steinberg is a GP with special interests in musculoskeletal medicine, evidence-based medicine and use of ultrasound. He's been reviewing topics for Health Navigator since 2017 and in his spare time loves programming. You can see some of the tools he's developed on his website.
Credits: Health Navigator Editorial Team . Reviewed By: Dr Jeremy Steinberg, FRNZCGP