D-mannose is an increasingly popular home remedy for recurrent UTIs.
Probably the most well known home remedies are cranberry supplements or cranberry juice.
How does D-mannose compare to this old favourite and is there any evidence that it really works?
What is D-mannose?
D-mannose is a simple sugar, closely related to the glucose found in many fruits (including cranberries) and in some vegetables. It is rapidly absorbed, but the human body can’t metabolize or store this sugar, so it is removed by the kidneys after about 30 mins, sent to the bladder and then released in the urine.
Although the number of studies on D-mannose and UTIs is relatively small, there are some encouraging results which make it a molecule of real interest.
Some studies suggest that D-mannose may be effective prophylactically for some cases and help to prevent urinary tract infections. Other studies show that D-mannose primarily reduces the severity of the symptoms experienced. There are also some which compare its effectiveness against commonly used antibiotic therapies.
How does D-mannose work?
UTIs are commonly caused when bacteria grow inside the bladder, causing an infection. Bacteria which commonly cause UTIs such as E. coli (responsible for about 90% of UTIs), have a cell structure which makes them good at hanging around in the bladder.
These bacteria get a foot hold by sticking to the bladder wall using hair-like projections on their cell surface called pili.
If they are unable to stick to the bladder wall, they struggle to build up in sufficient numbers to cause an infection, and this seems to be where D-mannose molecules comes in.
If they are present in the bladder, E. coli appears to bind with the D-mannose molecules rather than the bladder wall and are flushed from the bladder during urination.
Are there natural sources?
Several fruits and vegetables contain D-mannose, including:
- cranberries (and cranberry juice)
- green beans
Increasing these foods in your diet will certainly help if you are troubled with UTIs, but quantities in natural sources are relatively low. For example D-mannose makes up just 0.04% of the dry weight of cranberries. Needless to say, you would need to eat an awful lot cranberries for your body to get enough into your system to be effective. This is one of the main reasons that supplements are becoming increasingly popular.
How do I use D-mannose?
There are a lot of different D-mannose products on the market. The most popular forms are capsules and powders. Whilst capsules are more convenient for most, some people prefer powders because they avoid the fillers included in many capsules and can be easily dissolved in water
. Before you decide which to use, you should consider two things:
- whether you’re trying to prevent an infection or treat an active infection
- the dose you’ll need to take
The best dose to use isn’t entirely clear. For now, we suggest using the doses that have been used in research:
- For preventing frequent UTIs: 2 grams once daily, or 1 gram twice daily (diluted in 200ml of water if taken a s a powder)
- For treating an active UTI: 1.5 grams twice daily for 3 days, and then once daily for 10 days; or 1 gram three times daily for 14 days
It is also important to keep in mind that many products provide 500-milligram capsules. This means that you may need to take two to four capsules to get the appropriate dose.
Is it safe to take?
D-mannose is well tolerated by most people. Most don’t experience side effects, but some might have bloating, loose stools or diarrhoea.
It is important to note that there have been no studies done to confirm whether D-mannose is safe during pregnancy or breastfeeding, so you should be cautious if you fit into either of these groups.
If you have diabetes, it makes sense to be cautious as D-mannose is a sugar. Talk with your doctor before taking this supplement. Your doctor may want to monitor your blood sugar levels more closely if you decide to take it.
Most importantly, if you have an active UTI, don’t delay in talking with your doctor. Although D-mannose might help reduce the severity of your symptoms, there is little evidence at this point that it will effectively treat the infection. Delaying effective antibiotic treatment could result in a more serious infection spreading into the kidneys and blood.
More research needs to be done, but D-mannose does appear to show real promise for treating and preventing UTIs, especially in people who have frequent infections.