Cranberry

Abstract

Cranberry (Vaccinium macrocarpon) is an evergreen bush native to North America that belongs to the family Ericaceae. Cranberry products have been used to prevent and treat urinary tract infections (UTIs). Cranberry contains A-type proanthocyanidins (PACs), and epicatechin is the primary PAC found in cranberry extracts. Evidence suggests that cranberry blocks bacterial adhesion, especially Escherichia coli, to the uroepithelium of the urinary tract.1Howell AB Mol Nutr Food Res. 2007; 51: 732-737Crossref PubMed Scopus (205) Google Scholar For prevention of UTIs, the dosage of cranberry juice is 300 to 900 mL per day. Encapsulated cranberry formulations at a dosage of about 400 mg twice daily may be preferred. In general, products should deliver at least 36 mg of PACs for activity.2Howell AB et al.BMC Infect Dis. 2010; 10: 94Crossref PubMed Scopus (175) Google Scholar An ex-vivo study of urine samples from 32 healthy volunteers has shown the presence of prolonged urinary anti-adhesive activity when taking 72 mg of PACs daily.2Howell AB et al.BMC Infect Dis. 2010; 10: 94Crossref PubMed Scopus (175) Google Scholar The efficacy of cranberry is likely based on the PAC content, and negative studies might be due to inadequate amounts present. Multiple cranberry products are available, including cranberry juice cocktail, which is about 30% pure cranberry juice and contains sugar. Its beneficial effects are unknown. Study data on the adverse effects of cranberry products are limited. Cranberry juice and supplements may cause stomach upset and diarrhea. Ingesting large quantities of cranberry may increase the risk of developing kidney stones. A study of five healthy individuals who ingested cranberry concentrate tablets had an average 43% increase in urinary oxalate excretion.3Terris MK et al.Urology. 2001; 57: 26-29Abstract Full Text Full Text PDF PubMed Scopus (95) Google Scholar Anecdotal reports have suggested that cranberry may interact with warfarin, although recent studies found that it did not induce or inhibit CYP1A2, CYP2C9, or CYP3A4 enzyme systems.4Mellen CK et al.Br J Clin Pharmacol. 2010; 70: 139-142Crossref PubMed Scopus (22) Google Scholar Studies of cranberry have had mixed results. A 2012 Cochrane review of 24 studies concluded that use of cranberry products does not significantly reduce the overall risk of UTIs or its risk in subgroups of women or children with recurrent UTIs, older adults, pregnant women, patients with cancer, and catheterized patients. Long-term use of cranberry juice was not well tolerated, potentially resulting in high dropout rates in studies.5Jepson R et al.Cochrane Database Syst Rev. 2012; 10CD001321PubMed Google Scholar Randomized, controlled studies published since the Cochrane review have reported usefulness in preventing UTIs in women with recurrent infections, in patients at high risk of UTIs in long-term care settings, and after gynecological surgery requiring catheterization. A 2017 systematic review and meta-analysis evaluated the efficacy of cranberry on preventing recurrent UTIs in otherwise healthy, nonpregnant adult women. Data were extracted from earlier systematic reviews and an analysis of studies between 2011 and 2017. Seven studies with almost 1,500 women were identified, and one study had a large dropout rate. Overall, cranberry use was associated with a 26% reduction in recurrent UTIs in this healthy population.6Fu Z et al.J Nutr. 2017; 147: 2282-2288Crossref PubMed Scopus (42) Google Scholar In 2019, the American Urological Association made a conditional recommendation based on level C evidence that clinicians may offer cranberry for prophylaxis of recurrent UTIs.7www.auanet.org/guidelines/recurrent-utiGoogle Scholar Part of the rationale for this recommendation was recognition of the risks associated with overuse of antibiotics. Cranberry has also been evaluated for its effects on bacteriuria plus pyuria in a study of 185 female nursing home residents. Although investigators did not find benefits with cranberry compared with placebo, only about one-third of residents actually had the condition at baseline.8Juthani-Mehta M et al.JAMA. 2016; 316: 1879-1887Crossref PubMed Scopus (60) Google Scholar Current evidence does not support the use of cranberry products to treat UTIs. These patients should be referred to their primary care provider (PCP) for appropriate treatment. Many studies have evaluated the effect of cranberry products to decrease the risk of recurrent UTIs. Although results have been mixed, some of the variability may be due to use of products with an inadequate PAC content. Advise patients with a prior history of kidney stones to talk with their PCP or urologist before using cranberry products.