• Female, post-menopausal, age 55 years or older
• History of recurrent urinary tract infections with 3 or more symptomatic culture-proven episodes in 12 months or 2 or more in 6 months
• Currently free from urinary tract infection symptoms and negative urine culture
• Able to attend all follow-up appointments during the study
• Negative upper and lower urinary tract evaluation including pelvic exam (prolapse less than stage 2), post-void residual less than 50 ml, and imaging to exclude kidney stones, hydronephrosis, reflux, or urethral diverticulum

• Current use of D-mannose (must stop and complete 4-week washout to join)
• Complicated urinary tract infections requiring catheter use or with neurogenic bladder, bladder augmentation, or urinary diversion
• Use of other supplements listed in Box 1 (must stop and complete 4-week washout to join)
• Evidence of upper urinary tract infection such as fever over 38°C or flank pain
• Diagnosis of interstitial cystitis or overactive bladder syndrome
• Use of prophylactic antibiotics started in last 3 months and unwilling to stop, or intention to start in next 12 months
• Use of Uromune or other vaccines for recurrent UTI
• Participation in other investigational product studies in past 12 weeks
• Receipt of phage treatment
• History of chronic diarrhea requiring regular treatment
• Inability to swallow or gastrointestinal malabsorption
• History of recurrent vaginal yeast infections
• Systemic diseases preventing enrollment including uncontrolled diabetes (HgA1C above 7), ongoing chemotherapy or immunotherapy, renal insufficiency (creatinine > 1.5 g/dl), cognitive impairment, or restrictive diets requiring large fluid intake
• Nursing home residents
• Body mass index over 40

Box 1 Supplements to avoid:

• Multi-vitamins and multi-mineral capsules
• Specific vitamins or minerals (e.g., calcium, vitamin A, D, niacin, selenium, vitamin E, iron, omega 3, magnesium, B-complex)
• Probiotics
• Cranberry mannose or cranberry extract
• Weight loss products like Medifast, Vitafusion, OptiVin, appetite suppressants, Keto-Fuel