D-mannose is a naturally occurring sugar found in various fruits and also synthesized in the human body. It has gained attention as a potential treatment and preventative measure for urinary tract infections (UTIs). Some research indicates that D-mannose supplements may help prevent certain bacteria from adhering to the walls of the urinary tract, thus preventing infection. This article examines D-mannose, its potential benefits, side effects, and the current state of research regarding its effectiveness, especially in relation to UTIs.
What is D-Mannose?
D-mannose is a monosaccharide, a type of sugar related to glucose. It is present in many fruits, including apples, grapes, watermelon, cranberries, oranges, and peaches. D-mannose is also synthesized in the human body from glucose and is involved in the synthesis of glycoproteins. It plays a role in the glycosylation of certain proteins, which are post-translational modifications.
Other names for D-mannose include:
- Carubinose
- D-manosa
- Mannose
- Seminose
Potential Uses of D-Mannose
D-mannose is used for an inherited disorder called carbohydrate-deficient glycoprotein syndrome type 1b. Taking D-mannose by mouth can improve digestive problems, low blood sugar, and blood clotting disorders in people with this condition. It's not clear if it helps prevent liver problems.
Some people believe D-mannose may help treat UTIs by making it more difficult for the bacteria responsible for UTIs to attach themselves to the urinary tract.
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D-mannose is also used for UTIs, but there is no good scientific evidence to support this use.
Some studies suggest D-mannose may also play a useful role as a "prebiotic." Prebiotics are substances that may help your body by stimulating the growth of "good" bacteria in your digestive system. In some lab studies and studies in mice, D-mannose components were shown to increase the growth of "good" bacteria. This suggests D-mannose may have some use for people with dysbiosis, an imbalance in good and bad bacteria.
Understanding Urinary Tract Infections (UTIs)
UTIs occur when bacteria infect a person’s urinary tract, which includes the kidneys, bladder, and urethra. The most common UTI occurs in a person’s bladder, sometimes called cystitis. UTIs are more likely to affect women than men due to anatomical differences. Women are at a higher risk for UTI due to a short urethra located close to the rectum, which allows easier access for bacteria to the urinary tract as compared to men. Changes in sexual activity, pregnancy, and menopausal status also have a high impact on the risk for UTI occurrence since all of them affect the urogenital bacterial composition.
Common UTI Symptoms
UTIs can cause several uncomfortable and disruptive symptoms, including:
- Pain or burning when urinating
- A frequent urge to urinate
- Feeling tired, shaky, or confused (especially for older adults)
- Cloudy or foul-smelling urine
It is common for UTIs to recur, with 40 percent of women getting another UTI within 6 months of the previous one.
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The Role of Bacteria in UTIs
Uropathogenic Escherichia coli (UPEC) is the main causative organism of UTIs, accounting for up to 85% of cases. These bacteria enter the urogenital tract from the gut via the fecal-perineal-urethral route. UPEC strains possess virulence factors, such as adhesins, toxins, iron acquisition factors, lipopolysaccharides, and capsules, that contribute to UTI pathogenesis. One of the main disease-causing mechanisms for UPEC is its adherence to mannosylated protein components called uroplakins on the bladder epithelium. This binding occurs via the FimH tip of the type I pili adhesin of E. coli.
D-Mannose and UTIs: The Potential Connection
The interest in D-mannose and UTIs dates back to the 1970s, sustained by the emergence of antibiotic resistance related to uropathogens, especially UPEC. The rationale behind using D-mannose for UTIs lies in its ability to potentially interfere with the adhesion of bacteria to the urinary tract walls.
How D-Mannose May Work
The primary mechanism of action for D-mannose in preventing UTIs is thought to be through competitive inhibition. Here's how it works:
- Blocking Adhesion: E. coli bacteria attach to the cells lining the urinary tract using small, finger-like projections called fimbriae. These fimbriae have a protein called FimH at their tips, which binds to mannose molecules on the surface of the urinary tract cells.
- D-Mannose as a Decoy: When D-mannose is ingested, it is excreted in the urine. The presence of free D-mannose in the urine can saturate the FimH structures on E. coli, blocking their ability to adhere to the urinary tract epithelial cells.
- Flushing Out Bacteria: By binding to the FimH adhesins, D-mannose prevents the bacteria from sticking to the urinary tract walls. The bacteria are then flushed out of the body during urination, reducing the risk of infection.
Research on D-Mannose and UTIs
Some research suggests that D-mannose may play a part in treating active UTIs and preventing them from developing in the future.
Indeed, a 2022 study found that D-mannose effectively treated acute uncomplicated UTIs and prevented recurrent UTIs, with similar results to antibiotics, in several studies. Another 2022 review suggested that while antibiotics are likely to remain the first choice for UTIs, supplementing with D-mannose may increase treatment success.
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However, more recently, a 2024 study concluded that D-mannose supplements should not be recommended to prevent UTIs. Researchers tested whether it could help prevent recurrent urinary tract infections (UTIs) in women with frequent UTIs. Two groups were randomly given d-mannose or a placebo and monitored for six months. However, 51% of the women taking d-mannose and 56% of those taking the placebo still contacted their doctor for UTI treatment during the study.
Ultimately, the findings about D-mannose are inconsistent and more studies are necessary to determine whether it is a useful treatment for UTIs.
D-Mannose as an Alternative to Antibiotics
People with recurrent UTIs may need a low dose of antibiotics daily to prevent infection. According to a 2024 study, however, there is a risk that long-term antibiotic use will increase the likelihood of bacteria becoming resistant to antibiotics. Gram positive bacteria have demonstrated an alarming increase in resistance in recent years, especially to antibiotics like levofloxacin and penicillin, and even to backup options like vancomycin.
For this reason, scientists are trying to develop nonantibiotic treatments for common bacterial infections, such as UTIs. D-mannose may be one possible treatment.
Meta-Analyses and Systematic Reviews
A systematic review of research publications that met eligibility criteria in adult women showed possibly similar effectiveness as antibiotics.
Potential Side Effects and Risks
When taken by mouth: D-mannose is possibly safe for most adults when taken for up to 6 months. It can cause diarrhea and nausea. There isn't enough reliable information to know if D-mannose is safe or what the side effects might be when taken for more than 6 months.
D-mannose appears to be generally well tolerated in people.
Side effects of D-mannose may include:
- Bloating
- Loose stools
- Diarrhea
- Nausea
High doses of D-mannose may cause kidney damage.
Special Precautions and Warnings
There isn't enough reliable information to know if D-mannose is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.
D-mannose is possibly safe when taken by mouth in children with an inherited disorder called carbohydrate-deficient glycoprotein syndrome type 1b. It can cause diarrhea, loose stools, bloating, and nausea in these children. There isn't enough reliable information to know if D-mannose is safe to use in children who do not have this condition.
D-mannose supplements should be used with caution if you have diabetes. It may make it harder to control your blood sugar.
Interactions
As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
Dosage and Administration
Due to the lack of research to date, it is difficult to determine either the right dosage of D-mannose or the form in which people should take it. It is likely that the correct dosage for treating an active UTI will differ from that for preventing UTIs from recurring.
Some studies indicate that a dose level of 0.2 g/kg of body weight seems to be the upper limit for daily consumption of D-mannose for long-term use, as higher doses may cause gastrointestinal disturbances. However, further research on the optimal dosage is necessary. As a result, it is advisable to speak with a doctor before taking D-mannose supplements.
Sources of D-Mannose
D-mannose supplements are taken by mouth.
D-mannose is found naturally in high amounts in many fruits. Such fruits include:
- Apples
- Oranges
- Peaches
- Some berries such as blueberries and cranberries
Regulatory Status
Supplements are not regulated by the FDA the same way that medications are.