Hypothesis / aims of study
Different strains of bacteria may colonize the gut based on dietary factors. Over the past two decades, antibiotic consumption has doubled—70% of which is used in animal husbandry—allowing resistant bacteria to enter the food chain. As a result, individuals who consume meat may be more likely to harbor antibiotic-resistant bacteria as part of their fecal flora, with those who eat a plant-based diet harboring less virulent strains. We hypothesize that female vegetarians and vegans have a lower rate of recurrent UTI (rUTI) compared to non-vegetarians.
Study design, materials and methods
We performed a cross-sectional study of participants in the Adventist Health Study-2 (AHS-2) from whom detailed dietary and urinary history were collected[1]. Participants were classified as vegan, lacto-ovo-vegetarian, pesco-vegetarian, and non-vegetarian. Within the AHS-2 study, there was also an assessment of UTI history. Other variables included were: age, BMI, race, diabetes and menopausal status.
Results
57,252 women had complete data. Average age was 58 years. More than half (53.7%) of participants were non-vegetarian, 28.5% lacto-ovo-vegetarian, 10.3% pesco-vegetarian and 7.5% vegan. A history of rUTI was reported by 13.1%. Risk of rUTI increased with age, non-Black race, higher BMI, diabetes and menopause. The rate of reported rUTI significantly varied with diet: the highest prevalence of rUTI was in non-vegetarians (14.2%), followed by pesco-vegetarians (13.5%), lacto-ovo-vegetarians (11.6%) and vegans (10.3%, p<.001).
On multivariate regression, age, race, diabetes and menopause remained significant factors associated with rUTI. Additionally, diet maintained a statistically significant association with rUTI, with lacto-ovo-vegetarians and vegans at lower risk than pesco-vegetarians and non-vegetarians.
Interpretation of results
To our knowledge, this is the first report of differences in the rate of recurrent UTI based on diet, with vegans (10.3%) and lacto-ovo vegetarians (11.6%) having a lower rate of reported rUTI compared to pesco-vegetarians (13.5%) and non-vegetarians (14.2%). As rUTI affects a substantial proportion of women experiencing bacterial cystitis, this finding may have important clinical relevance as these women are subject to repeat courses of antibiotics and are at particularly high risk of developing antibiotic-resistant infections.
The primary driver of antibiotic resistance is selective pressure from antibiotic overutilization. Animal husbandry is responsible for the vast majority of antibiotic consumption[2]. Entrance of resistant microorganisms into the food chain drives resistance in human commensal bacteria. Antimicrobial resistance in aquaculture similarly poses a substantial public health concern.
Antibiotic resistance is a risk factor for rUTI due to subtotal eradication of the infection and creation of a colonic reservoir of resistant bacteria. We hypothesize that because vegetarians avoid meat, a vegetarian diet may be associated with a lower risk of rUTI. It has recently been demonstrated that antimicrobial resistance patterns differ in vegetarians versus meat eaters. Higher intake of chicken is associated with cefotaxime resistance, and higher pork intake is linked to norfloxacin resistance[3]. In contrast, higher intake of vegetables and cheese is tied to a lower risk of amoxicillin and amoxicillin-clavulanic acid resistance.
Ultimately, future studies are likely necessary to decide if dietary change might affect rUTI patterns, including a prospective trial of dietary intervention as a means for rUTI prevention.