Researchers compared urinary bacteria levels of elderly women who drank 10 ounces of a juice drink containing cranberry juice each day to elderly women who consumed the same amount of a look-alike drink without cranberry juice (indistinguishable in taste, appearance, and vitamin C content from cranberry juice). 153 elderly women participated in this study. Each one was randomly assigned to the cranberry juice group or the placebo group and was followed over a 6-month period. The women had a mean age of 78.5 years and high levels of bacteria in their urine at the start of the study. The odds in the cranberry group of having bacteria levels exceeding a certain threshold were 42% of what they were in the control group. Which negative effect was not being controlled for by using the placebo drink