Five studies (n=436 participants; range 15 to 305) were included in the review: four randomised controlled trials (RCTs) and one pilot study. Two RCTs were cross-over in design, one RCT had a factorial design, and one pilot study had an open cross-over design. Some studies reported details of withdrawals and drop-outs.
Urinary tract infection prevention (four studies): Cranberry significantly reduced biofilm load compared to baseline (p=0.013; one cross-over pilot study). One RCT reported a reduction in the likelihood of urinary tract infections (p<0.05) due to a reduction in adhesion of Gram-negative (p=0.05) and Gram-positive (p=0.002) bacteria while receiving cranberry compared with placebo. The same study also reported a reduction in the incidence of significant bacteriuria for those receiving cranberry compared with placebo (p=0.01). There were no statistically significant differences between cranberry tablets and placebo for other urinary outcomes (two RCTs). Only two studies reported adverse reactions; these were reported to be mild (diarrhoea, constipation, nausea, rash, and abdominal discomfort).
Urinary tract infection treatment (one RCT): There were no significant differences between cranberry and placebo groups for urine specimens with bacterial counts, types and numbers of bacterial species, number of urinary leukocytes, urinary pH, or episodes of symptomatic urinary tract infection. Some participants appeared to withdraw from the intervention group due to adverse events (details not reported).