This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
D-mannose is often marketed as a dietary supplement that prevents urinary tract infections (UTIs). There is little research to support this. Researchers therefore compared D-mannose to a dummy supplement (fructose) in women seeking GP advice for frequent UTIs.
After 6 months, those taking D-mannose had:
- no reduction in suspected UTIs for which they contacted primary care
- no reduction in laboratory-confirmed UTIs
- no reduction in hospital admissions for UTIs.
D-mannose does not prevent UTIs among women with recurrent UTIs presenting to primary care, the authors conclude.
More information on urinary tract infections can be found on the NHS website.
The issue: is D-mannose helpful for UTIs?
Urinary tract infections (UTIs) affect the organs involved in peeing, including the bladder, urethra (the tube that allows urine to pass out of the bladder), and kidneys. They are more common in women than men; 1 in 2 women will have a UTI in their lifetime, and about 1 in 4 who have a first UTI will go on to have frequent, or recurrent, infections (2 in 6 months or 3 in a year). UTIs negatively impact women’s personal, social and working lives.
The National Institute for Health and Care Excellence (NICE) recommends daily, low-dose antibiotics as an option to prevent frequent UTIs in women. However, taking them long-term can increase the chance of bacteria becoming resistant, and the antibiotics ineffective. Other options include vaginal oestrogen and methenamine hippurate (an antiseptic drug, not an antibiotic). The guidelines note that some women self-care with cranberry products or D-mannose.
D-Mannose is a sugar found in some fruits and vegetables, and sold as a dietary supplement. It has been thought to stop bacteria that cause UTIs attaching to bladder lining cells. However, it is not prescribed on the NHS and there is little evidence to support its use.
Researchers assessed whether D-mannose prevents UTIs in women with frequent infections.
What’s new?
The study included 99 GP practices in England and Wales who invited women with recurrent urinary tract infections (UTIs) to take part. They ranged in age from 18 to 93; the average was 59 years. The majority (64%) were postmenopausal.
Half the women took 2 grams of D-mannose every day; the others took 2 grams of fructose sugar (control). The main outcome was the number who sought medical help for a suspected UTI within 6 months of the start of the study. 298 from the D-mannose group and 289 from the control group provided data for this outcome.
The researchers found that after 6 months, D-mannose made little difference to:
- the number of women who contacted a healthcare provider with suspected UTIs (51% D-mannose group; 56% control group)
- the number of hospital admissions for UTIs (2% D-mannose group; 1% control group)
- other secondary outcomes such as the number of laboratory-confirmed UTIs or courses of prescribed antibiotics.
The study included fewer pre- than postmenopausal women. However, the lack of effect of D-mannose on suspected UTIs was similar in pre- and postmenopausal women.
Why is this important?
The study suggests that D-mannose is not effective at preventing urinary tract infections (UTIs) in women who have frequent infections. Primary care clinicians could discuss these findings with women who are considering taking D-mannose.
This trial was designed to evaluate real life use of preventive medicines, including self-administration and missed doses.
Women measured out D-mannose and fructose using a scoop, so some may have taken more or less than was intended. More than 2 in 3 reported taking the D-mannose at least 3 days a week for 15 weeks of the study so some doses may have been missed.
What’s next?
The researchers have contacted NICE about their guidance on D-mannose.
You may be interested to read
This is a summary of: Hayward G, and others. D-Mannose for Prevention of Recurrent Urinary Tract Infection Among Women: A Randomized Clinical Trial. JAMA Internal Medicine 2024; 184: 619 – 628.
Information and support from Bladder Health UK.
A summary of a paper about another non-antibiotic alternative to prevent frequent UTIs in women.
Information on taking part in NIHR research on urinary tract infections.
Funding: This study was funded by the NIHR School for Primary Care Research. Christopher Butler received support as an NIHR senior investigator. Additional support was provided by the NIHR Health Protection Research Unit on Healthcare Associated Infections and Antimicrobial Resistance, the NIHR Oxford Biomedical Research Centre, and the NIHR Academic Clinical Lectureship programme.
Conflicts of Interest: None reported.
Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.
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