Research D-Mannose Side Effects

D-Mannose Side Effects

Preganant woman at Doctor's office

It is very important to ask questions about any supplement and its potential effects, D-Mannose is no exception. D-Mannose is recommended by the National Institute for Health and Care Excellence and doctors and chemists. As a natural supplement, it creates no bacterial resistance and has no damaging side-effects, and can be safely used as a maintenance product daily.

For nearly 70 years research has shown positive effects of D-Mannose on E. coli, the bacterium that accounts for 85-90% of Urinary Tract and Bladder Infections. Research papers and reports on D-Mannose and its symbiotic, Velcro like relationship with E. coli and evidence of how effective D-Mannose is at attaching to, and flushing bacteria out of the bladder are freely available online from credible sources such as the British Medical Journal

D-Mannose is a monosaccharide related to glucosamine that attaches to bacteria and then leaves the body when we urinate. D-Mannose uses the bacteria's best weapon against them. Microscopic fimbrial hairs produced by bacteria to attach to the D-Mannose naturally present in the bladder, attach like Velcro to the ingested D-Mannose in the urine. Once the fimbrial receptors are filled they helplessly float in the urine and are flushed away down the toilet. They can never become resistant.

Antibiotic Alternative

Antibiotics are now known to radically change the gastrointestinal bacterial populations required for good health, potentially causing fungal or bacterial infections, that is why doctors are suggesting we use antibiotics sparingly. Whereas D-Mannose does nothing other than remove 'bad' bacteria by process of attachment and voiding, without harmful side effects.

However, always play it safe and monitor:

  • Quality. It is very important to check the quality of mannose you are buying. No chemical residues, no additives and a guaranteed 99% purity are all essential safety features.
  • Symptoms. Keep a close eye on your symptoms. Use urine test strips to monitor nitrites, leukocytes and blood. If D-Mannose is not alleviating your symptoms, seek medical help as a bacterium other than E. coli may be present and could develop in to kidney infection.
  • SIBO. Small Intestinal Bacterial Overgrowth experts recommend avoiding D-Mannose while others say it is tolerated fairly well. A potential for exacerbation does exist, if you are affected, adjust the dose.

Corn Allergies

If you have a known corn allergy, pick a mannose that has certification that there are zero residues of corn in the final product, seek corn free D-Mannose or D-Mannose made from tree bark or plant matter.


D-Mannose is an isomer of glucose, not glucose, so is not metabolised to any discernible extent. It is a natural supplement and not a drug. It is widely considered to be safer than white table sugar. In over 70 years of use, there have never been any teratogenic effects shown. There are a couple of points to bear in mind:

  • D-Mannose is a rare sugar already present in some cells in the human body, we create it from glucose. Ingesting large amounts of D-Mannose may cause diahorrhea, because it flushes pathological E. coli out of the colon under these circumstances. It's probably best to stick to a dose level that can more easily be absorbed.
  • Always follow medical advice during pregnancy.

Genetic Disorders

Very rarely, people with genetic disorders such as MPI-CDG and PMM2-CDG or with difficulties digesting sugars may suffer complications, however pure D-Mannose without added sugars has virtually no glycogen impact. Again, check the purity and follow medical advice, particularly if this disorder is diagnosed during pregnancy.

Gas and Bloating

Gas or Bloating may be experienced by people when they first use D-Mannose. The most likely culprit is Leaky Gut and when the gut is restored to health, this problem usually resolves itself. In the meantime, taking D-Mannose with food and probiotics has been reported to help.

Conditions commonly associated with dysbiosis (an imbalance or good and bad bacteria in the gut) are asthma, food allergies, sinusitis, eczema, migraine, irritable bowel, candida overgrowth, obesity, fibromyalgia, and inflammatory disorders such as arthritis, fibroids and PMT. Overuse of antibiotics, anti-inflammatory drugs, poor diet and lack of exercise are seen as equally damaging to gut health.