The field of probiotics research has recently widened, and there are many potential applications to modulating gut microbiota. Gut microbiota can modulate the immune function, the brain network, and the gastrointestinal health. Other implications include asthma and atopy, as well as some cases of joint pain. But what about urinary tract infections?
According to recent evidence, probiotics could be useful to modulate the recurrence of urinary tract infections. What is the mechanism behind this finding? Is the evidence convincing according to the scientific literature?
Microbiota function in different tissues
We live in constant interaction with our environment, and microbiota in different tissues is a perfect example. In the skin, mouth, gastrointestinal tract, urinary tract and vagina, we have millions of microorganisms constantly moving around, colonizing areas, and competing with each other. This interaction is usually balanced, and instead of creating problems, these bacteria contribute to preserving our health.
Dysbiosis refer to an imbalance of the microbiota, and this term is usually applied to the gut. However, we can have an imbalance in the urinary tract, the vagina, the mouth and the skin. One clear example of this is bacterial vaginosis, an infection that appears when the proportion of bacteria in the vagina changes abruptly. There’s an overgrowth of certain bacteria, and they cause uncomfortable symptoms that include vaginal discharge, itching and a foul odor.
The urethra has a distinct microbiota, too. In women, it is usually associated with the microbiota in the vagina. In the urogenital tract, the urethra usually has corynebacteria, staphylococci, and some enteric bacteria. In the vagina we usually have lactic acid bacteria and many other in a mixed and very heterogeneous group.
In healthy people, the urine should always be sterile, but when it goes through the urinary tract it flushes and drags microorganisms from the urethra. Colonization in the urethra is not as abundant as in the gut or the vagina, and in most cases fecal contaminants and vaginal infections are the main causes of recurring urinary tract infections in women. However, studies have evaluated the microbiota of the urethra and the vagina, reporting that a healthy microbiota and an abundance of lactic acid bacteria may significantly reduce the recurrence of UTI.
How gut microbiota relates to other tissues
The microbiota of the gut has a direct or indirect relationship with many other tissues in the human body. The gut is associated with the largest lymphoid tissue in the human body, known as gut-associated lymphoid tissue, or GALT. Circulating white blood cells are in constant interaction with the gut microbiota. Gut bacteria display or release membrane proteins detected by white blood cells, and they activate a signaling system that keeps the immune system active and on guard against potential threats.
The gut microbiota may also produce different enzymes and molecules that contribute to the metabolism of the body, even in distant organs such as the brain and the liver. More recently, various studies have evaluated a possible interaction between the gut microbiota and the urinary tract, which is why probiotics are recently proposed as a way to reduce the incidence of UTI, especially in people with recurrent infections.
The rationale of using probiotics is even more clear if we take in consideration the use and abuse of antibiotics, which is a debated topic in modern medicine. Antibiotics are administered to fight infection in a given tissue, but in most cases they have a widespread influence in almost every tissue with a healthy flora. What was initially meant to destroy bacteria in the lungs may ultimately cause a dysbiosis in the intestines and the skin, causing side effects such as diarrhea and skin rash.
A dysbiosis in the urinary tract and when the vagina does not have enough lactobacillus species, UTI become more common and recurrent. There are two different ways of using probiotics for UTI, as vaginal suppositories or as oral probiotics. Vaginal suppositories appear to be the simplest way, and it may be difficult to understand why oral probiotics can also do the trick. But they do, even if there’s not a clear understanding of the exact mechanism.
Can probiotics prevent UTI?
Many clinical trials have evaluated the role of probiotics in UTI. They usually recruit women because they are usually more susceptible than men to experiencing recurrent urinary tract infections. In some cases, clinical trials use vaginal suppositories with lactobacilli, but other studies use oral probiotics.
In a recent trial, probiotics reduced the rate of recurrence of UTI from 27% in the placebo group to 15% in the group of women receiving probiotics. The risk reduction is clear and evident, even in oral probiotics. According to a clinical trial, administering oral probiotics may also modulate the colonization of the vagina. This may be due to a signaling in the immune system or a mechanism that still eludes modern science, but the results are clear and reproducible.
Still, to prevent UTI we should not limit ourselves to probiotics. There are many other health measures we can also take to further reduce the recurrence of urinary tract infections:
- Detect and avoid incorrect hygiene techniques, which is a common cause of recurrent UTI in women and children
- Evaluating the possibility of kidney stones in males and females
- Ruling out sexually-transmitted diseases and prostate issues, which may cause urinary tract symptoms in men and women
- Being careful to complete antibiotic therapy as prescribed by your doctor. Remember that not complying may lead to antibiotic failure and bacterial resistance.
- You can also try other herbs and supplements that work for UTIs, such as uva ursi, garlic, cranberry juice, and D-mannose.
Schmiemann, G., Kniehl, E., Gebhardt, K., Matejczyk, M. M., & Hummers-Pradier, E. (2010). The diagnosis of urinary tract infection: a systematic review. Deutsches Ärzteblatt International, 107(21), 361.
Reid, G., Beuerman, D., Heinemann, C., & Bruce, A. W. (2001). Probiotic Lactobacillus dose required to restore and maintain a normal vaginal flora. FEMS Immunology & Medical Microbiology, 32(1), 37-41.
Naber, K. G., Bergman, B. O., Bishop, M. C., Bjerklund-Johansen, T. E., Botto, H., Lobel, B., … & Selvaggi, F. P. (2001). EAU Guidelines for the Management of Urinary and Male Genital Tract Infectionstextsuperscript1. European urology, 40(5), 576-588.