American cranberry (vaccinium macrocarpon) was used medicinally by native americans for the treatment of bladder and kidney ailments. a randomized controlled study was designed to test whether regular drinking of cranberry juice can prevent the recurrence of urinary tract infections (utis) in women. one hundred and fifty women with a urinary tract infection were treated with an antibiotic and then randomly assigned to one of 3 groups. one group drank cranberry juice concentrate daily for six months; another group took a drink containing lactobacillus (a lactose-fermenting bacterium thought to inhibit the growth of uti-causing bacteria) daily for six months; the last group served as the control group and drank neither cranberry juice nor lactobacillus drinks for six months. after six months, the number of women in each group with recurring symptomatic urinary tract infection (defined as one or more new infections) was recorded. here are the results.