Cranberry for UTIs: not just folklore
- Cranberry most beneficial for women with recurrent UTIs
- Twice-daily dosing key to benefit
- More dose-response studies of cranberry needed
Cranberry-containing products may be more than just a folk remedy for urinary tract infections (UTIs). A systematic review and meta-analysis published in the Archives of Internal Medicine concludes that cranberry-containing products offer women protection against UTIs, particularly those prone to recurrent infections.
Researchers from Taiwan reviewed 13 randomized, controlled trials involving over 1,600 men, women, and children of different populations including the elderly; the hospitalized; those with neuropathic bladder, spinal cord injuries, or multiple sclerosis; and pregnant women. Most of the trials (10) were conducted in North America; the remainder were conducted in Finland, Italy, and the United Kingdom.
Cranberry-containing products used in the studies took on different forms, dosages, and A-type proanthocyanidins (PAC) content; PAC is a substance identified as potentially having the ability to inhibit Escherichia coli from adhering to the urogenital mucosa. Nine of the trials looked at cranberry juice, while 4 used capsules or tablets. Daily cranberry dose ranged from 0.4 to 194 .4 g. In most of the trials, researchers administered the cranberry products for a period of 6 months.
The authors of the review concluded that cranberry-containing products are most protective against UTIs in women with recurrent infections. They also may offer protection to women in general, including those who are pregnant, and to children and other populations, but heterogeneity across the trials made interpretation difficult.
Cranberry juice was more effective than capsules or tablets, but the investigators noted that could be because women who drink cranberry juice are better hydrated. They also found that dosing at least twice daily seems necessary to achieve benefit. Only 1 study looked at dose-response and found that higher doses of cranberry juice were associated with fewer UTIs. The researchers noted that more dose-response studies are needed.
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