Does cranberry work for UTIs?

A Cochrane review found cranberry products reduce recurrent UTI risk in susceptible women by around 25 percent. It is prevention only — cranberry does not treat an active infection.

Are probiotics useful with antibiotics?

Yes. Meta-analyses show meaningful reductions in antibiotic-associated diarrhoea and Clostridioides difficile infection, particularly with Saccharomyces boulardii and Lactobacillus strains.

Can vitamin C prevent bacterial infections?

Vitamin C has modest evidence for shortening colds, which are viral. There is no good evidence it prevents bacterial infection in well-nourished people.

Immune

Moderate Evidence

Bacterial Infection Prevention

Protection against harmful bacterial colonization.

TL;DR

Cranberry proanthocyanidins reduce recurrent urinary tract infections, and probiotics reduce antibiotic-associated and hospital-acquired infections. Nothing here substitutes for antibiotics in an active infection.

Why It Matters

Barrier integrity, mucosal immunity and colonisation resistance from a healthy microbiome determine whether pathogenic bacteria establish. With antimicrobial resistance rising, prevention strategies with real trial support have genuine value — recurrent UTI prophylaxis is the clearest example. Suspected bacterial infection with fever, rapidly worsening symptoms, or confusion requires urgent medical care, not supplements.

How to Measure

Test for infections, not for prevention: urine culture for suspected UTI, full blood count with differential, CRP and procalcitonin where sepsis is a concern. For prevention, monitor 25-OH vitamin D and zinc status, since deficiency in both impairs mucosal defence.

Biomarkers

25-OH vitamin D

Serum zinc

Urine culture

White cell count with differential

CRP

Optimization Protocol

Basics dominate: handwashing, dental hygiene, wound care, and staying current with pneumococcal and influenza vaccination. Correct vitamin D deficiency and zinc deficiency, both of which impair epithelial and mucosal defence. For recurrent UTI, cranberry extract standardised to 36 mg proanthocyanidins daily plus 2-3 L fluid. Take a multi-strain probiotic providing 10-25 billion CFU during and after any antibiotic course, separated by two hours. Do not treat an established bacterial infection with supplements.