Cranberry and urinary tract infections: state of scientific knowledge
The term "urinary tract infections” (UTIs) covers a heterogeneous group of infections occurring more frequently in women than in men, with 40 to 50% of women having at least one UTI during their lifetime. The bacterium Escherichia coli (E. coli) is the pathogen most frequently responsible for UTIs in women aged from 15 to 65 years (80% of cases).
Questions have been raised for several years about the possibility of using cranberry and products containing it to prevent UTIs. Various risk assessment agencies have examined it in the fields of both nutrition and health products:
- between 2003 and 2008, the French Food Safety Agency (AFSSA) assessed various cranberry products for which numerous claims had been made suggesting a direct link between consumption of cranberry and prevention of UTIs;
- in 2008, the French Health Products Safety Agency (AFSSAPS) addressed this issue in its guidelines entitled “Diagnostic et antibiothérapie des infections urinaires bactériennes communautaires chez l'adulte” ["Diagnosis and antibiotic treatment of community-acquired bacterial urinary tract infections in adults"];
- in 2009, the European Food Safety Authority (EFSA) assessed the claim “Helps reduce the risk of urinary tract infection in women by inhibiting the adherence of certain bacteria in the urinary tract” related to a cranberry juice and to dried cranberries.
All these assessments are consistent and indicate that:
- cranberry products reduce the adherence of certain bacteria that cause UTIs to the urinary tract walls.
Experimental studies do indeed show that cranberry products (juice, cocktails or juice extracts) or urine from subjects who consumed these products inhibit the adherence of certain E. coli bacteria to uroepithelial cells. This effect is related to the presence in cranberry products of antioxidants called proanthocyanidins (PACs) that are responsible for the anti-adherence effect.
- however the data, which include clinical data (from patient monitoring), are currently insufficient to conclude that consumption of cranberry, or products containing it, has a preventive effect on UTIs.
Some of the available studies showed no effect of cranberry consumption on the recurrence of UTIs, whereas others reached no conclusion due to lack of data. Furthermore, most of the results showing a positive effect of cranberry consumption on the occurrence and prevention of UTIs cannot be taken into account due to methodological weaknesses in the studies.
For example, in 2003 AFSSA considered as acceptable the claim "Helps to reduce the adherence of certain E. coli bacteria to the urinary tract walls” on the basis of studies conducted with several cranberry products providing 36 mg of cranberry PACs.
At the same time, press articles and advertisements stating that consumption of cranberry products could help prevent or even cure UTIs, some improperly referring to an AFSSA opinion, were published widely.
Lastly, the Directorate General for Competition, Consumer Affairs and Fraud Control (DGCCRF) specified in a memo, in early 2011, the analytical method to be used to determine the PAC content of cranberry products.
In this context, the Agency issued an internal request on 15 September 2010 in order to update its work, mainly to determine whether new studies help to clarify the effect of cranberry consumption on UTI prevention. This new assessment will also clarify the context for using the claim validated in 2003, thus avoiding any misuse or misrepresentation.
For the new opinion that it is issuing today, ANSES reviewed ten studies published since its previous opinions. This work reaffirms the findings issued by the Agency in the past.
The experimental data obtained in vitro show that the PACs found in cranberry have an inhibitory effect on the adherence of certain bacteria that cause UTIs (E. coli) to the urinary tract epithelial cells. However, the clinical data currently available are insufficient to conclude that consumption of cranberry has a preventive effect on UTIs. Such a claim would be improper in the light of current knowledge.
ANSES notes that the clinical trials assessing the effect of cranberry consumption often have methodological weaknesses, particularly in terms of the limited number of subjects and/or lack of a placebo. Considering cranberry's potential value if its effect in preventing UTIs were proven, ANSES will continue to monitor scientific developments on this topic.
The Opinion of 18 March 2011 on the assessment of the potential effects of cranberry on community-acquired urinary tract infections
- Opinion of 29 August 2003 (in French) on the assessment of evidence concerning the claim "helps maintain healthy urinary tract through a significant reduction in the presence of germs" and the use of cranberry or Vaccinium macrocarpon in juice concentrates, dietary supplements and a juice cocktail/nectar
- Opinion of 6 April 2004 (in French) on the assessment of evidence concerning the claim "Helps to reduce the adherence of certain E. coli bacteria to the urinary tract walls" and on the use of cranberry or Vaccinium macrocarpon in juice concentrates, dietary supplements and a juice cocktail/nectar
- Opinion of 3 December 2004 (in French) on the assessment of evidence concerning the claim "helps to reduce the adherence of certain E. coli bacteria to the urinary tract walls" for a cranberry juice cocktail/nectar
- Opinion of 14 June 2007 (in French) on the assessment of evidence concerning the extension of the claim "helps to reduce the adherence of certain E. coli bacteria to the urinary tract walls" on the use of cranberry or Vaccinium macrocarpon in fresh and frozen cranberry, cranberry puree, dried/sweetened cranberries and dried/sweetened flavoured cranberries
- Opinion of 30 January 2008 (in French) on the assessment of enrichment with vitamins C and E of a fruit-based (including cranberry) beverage presented as intended for people aged 65 and over (seniors) as well as its associated claims