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Tuesday, 6 October 2026dailybeirut.com
Health
A new study reveals that individual differences in urinary metabolism determine whether cranberry juice effectively prevents UTIs in healthy women.
Differences in how women metabolize compounds and their natural urinary defenses may explain why cranberry juice prevents infections in some individuals but fails in others. A recent trial published in the journal Nutrients identified distinct baseline anti-adhesion activity levels and varied responses to cranberry intake among healthy women, highlighting the role of metabolic phenotyping in personalized nutrition.
Urinary tract infections affect 60% of women at some point in their lives, with an annual prevalence of 10%. More than 90% of diagnosed cases are caused by uropathogenic Escherichia coli (UPEC) possessing P-type or type 1 fimbriae. P-fimbriated UPEC initiate infection by adhering to epithelial cells in the urinary tract. These structures are present in nearly all, and potentially all, UPEC strains responsible for acute pyelonephritis and urosepsis in otherwise healthy individuals.
P fimbriae enable strong binding to glycolipid receptors on uroepithelial cells. This adhesion is robust enough to withstand the constant flow of urine, facilitating successful colonization. Cranberry juice has been reported to inhibit this adhesion by P-type UPEC, a benefit largely attributed to its content of A-type procyanidins. However, clinical trials have produced inconsistent results, leading researchers to hypothesize that metabolic differences among women influence the degree of change in urinary anti-adhesion activity following consumption.
The screening trial included 152 healthy women aged 21 to 65 years, with 150 completing the intervention and post-consumption collection. Most participants were between 21 and 35 years old. The demographic breakdown showed approximately 60% non-Hispanic or Latino, 20% Asian, 6% African American, and 12.5% Hispanic/Latino individuals.
Participants avoided all cranberry products, specified polyphenol-rich foods, dietary supplements, alcohol, coffee, and tea for 10 days. They then consumed 10 ounces of pure cranberry juice daily for four days while maintaining other dietary restrictions. Urine testing occurred at baseline on days 9 and 10, and post-intervention on day 15. The study aimed to evaluate urinary anti-adhesion capacity using fluorometry to yield anti-adhesion indices (AAI). Researchers compared metabolite profiles from 18 baseline samples with high AAI against 18 samples with low AAI.
The unsweetened pure cranberry juice used contained anthocyanins, flavonols (primarily quercetin and myricetin), and procyanidins at levels about 2.5 times higher than those found in commercial 27% cranberry juice cocktails. Ten ounces provided 89.5 mg of procyanidins per day, exceeding the previously suggested minimum effective dose of 36 mg/day required to trigger urinary anti-adhesion activity.
Baseline urinary AAI against P-type UPEC ranged from 84 to 170. Seventy-seven women were classified as having a ‘UTI-susceptible’ phenotype because their baseline AAI was below the 50th percentile (AAI = 131). The remaining 75 were categorized as ‘UTI-nonsusceptible.’ The metabolome differed significantly between high- and low-AAI urine samples, with 165 discriminant metabolic features distinguishing the two groups.
After four days of intake, women showing positive AAI changes above 10 were labeled positive responders. The rest were non-positive responders. This group comprised 34.2% of UTI-susceptible women versus 18.9% of UTI-nonsusceptible women. Numerically, this equated to 26 out of 76 susceptible women and 14 out of 74 nonsusceptible women responding positively. The susceptible group had a statistically significant higher proportion of responders.
Authors suggest humans exhibit multiple metabolic pathways for cranberry compounds. For example, daidzein converts to equol in 25-30% of adults, while the remainder do not produce equol. Similarly, ellagitannins and ellagic acid convert to urolithin A in 25%-80% of adults, but 10%-50% also produce isourolithin A and/or urolithin B. About 5%-25% of individuals produce no urolithins. The gut microbiome is thought to explain much of this variation in metabolic phenotype.
Clear differences existed in the urinary metabolic profiles of women with high and low anti-adhesion activity. While 165 metabolic features distinguished the groups, identifying specific compounds proved difficult because most biological compounds are not represented in open mass spectral libraries. Only a small proportion could be tentatively identified.
Six metabolites were linked to higher anti-adhesion activity, including D-glucaro-1,4-lactone, an acylcarnitine, and several compounds related to dietary polyphenols. Five metabolites were associated with lower activity, including cysteine and alliin derivatives linked to the consumption of allium vegetables such as onions and garlic.
The study had limitations: participants were mostly younger due to college campus recruitment, and only anti-adhesion activity against P-type UPEC was assessed. Habitual dietary intake and physical activity patterns were not recorded. Cranberry juice was consumed for only four days, so acute or chronic effects were not assessed. Crucially, the trial did not measure whether participants subsequently developed UTIs, meaning laboratory phenotypes cannot yet be assumed to predict clinical risk or prevention.
Healthy women showed distinct interindividual differences in urinary anti-adhesion capacity against P-type UPEC at baseline and in response to cranberry juice. Individual metabolism differences may influence this variation and explain inconsistent findings in earlier trials. Further study is required to establish the effects of cranberries on the urinary metabolome and gut microbiome and to determine if these phenotypes predict clinical responses.
“This study suggests that women need personalized recommendations on whether to use cranberry products to prevent UTIs based on their individual metabolic phenotype,” the authors stated.
