What is D-Mannose?
D-Mannose is a monosaccharide, a component of various polysaccharides, and a sugar related to glucose. Similar to glucose, it can be naturally produced within the body and is found in some plants in the form of starch. Several fruits and vegetables contain D-Mannose, including cranberries, apples, oranges, peaches, cauliflower, and green beans. D-Mannose is also present in certain dietary supplements, often available in capsule or powder form.
D-Mannose plays an important role in human metabolism and is widely distributed in body fluids and tissues, particularly in the nervous system, skin, testes, retina, liver, and intestines. It is directly utilized in glycoprotein synthesis and has various physiological effects within the body, including:
- Regulating the immune system 
- Promoting wound healing 
- Exhibiting anti-inflammatory effects 
- Inhibiting tumor growth and metastasis 
- Preventing certain bacterial infections, such as urinary tract infections 
Evidenced Benefits and Advantages of D-Mannose
1. Treatment of Urinary Tract Infections
An increasing body of research suggests that D-Mannose may play a role in treating active urinary tract infections (UTIs) and preventing their progression. A study published in the World Journal of Urology in 2014 found that D-Mannose might effectively prevent further infections in individuals recovering from UTIs. In this study, D-Mannose was found to be more effective than the antibiotic nitrofurantoin.
Another study from 2016 also provided evidence that D-Mannose could be an effective treatment and preventive measure for urinary tract infections. Additionally, the United Kingdom National Institute for Health Research is currently funding research into the relationship between D-Mannose and recurrent UTIs    .
💡Evidence: In a study involving over 300 women with recurrent urinary tract infections, participants were divided into three groups: those receiving 2 grams of D-Mannose per day, those receiving 50 milligrams of antibiotics, and those receiving no treatment at all. The study spanned six months. Among the group taking D-Mannose, only 15% experienced urinary tract infections, compared to 20% in the antibiotic group and a higher rate in the no-treatment group. Furthermore, the incidence of side effects in the D-Mannose group was significantly lower than in the antibiotic group.
2. Congenital Disorders of Glycosylation (CDGS) – Phosphomannose Isomerase Deficiency
Phosphomannose isomerase deficiency is the cause of congenital disorders of glycosylation (CDGS), a condition resulting from mutations in the PMI1 gene. The clinical manifestations are characterized by protein-losing enteropathy, and supplementation with mannose appears to improve protein loss, liver function, hypoglycemia, and coagulation disorders in individuals affected by this disease. Other types of CDGS commonly exhibit neurological features, and using standard diagnostic procedures, this condition cannot be distinguished from CDGS type Ia (phosphomannose mutase deficiency)    .
3. Prebiotic Effects
Prebiotics and probiotics are considered natural alternatives to animal-produced dietary antibiotics. Plant extracts and yeast cell walls are products rich in mannose, which can serve as substrates for the adhesion of Gram-negative bacteria. In some laboratory and mouse studies, mannose components have shown to enhance the growth of beneficial bacteria, suggesting that mannose might have some utility for patients with imbalanced bacterial flora. Research indicates that mannose can induce the expression of pro-inflammatory cytokines and anti-inflammatory cytokines, providing evidence of its immunostimulatory properties     .
Are There Any Side Effects of D-Mannose?
D-mannose is generally considered safe since it naturally occurs in many foods. However, excessive consumption can lead to some adverse symptoms.
- Excessive intake of D-mannose can potentially cause diarrhea, loose stools, and bloating. High doses may also put strain on the kidneys.
- There is limited literature on the use of D-mannose during pregnancy and breastfeeding, and until experimental safety data is available, it’s advisable for pregnant and breastfeeding women to avoid using supplements.
- Some studies suggest that D-mannose might complicate blood sugar control for individuals with diabetes.
How to Take D-Mannose and What Dosage is Beneficial?
There is currently insufficient scientific evidence to determine the appropriate dosage range for D-mannose. For preventing recurrent urinary tract infections, experimental research suggests a daily dosage of 2 grams or 1 gram per dose (twice daily). For treating active urinary tract infections, the dosage is 1.5 grams per dose (twice daily) for 3 to 5 days.
D-mannose is available in capsule and powder forms, and the choice primarily depends on personal preference. Many products offer 500 mg capsules, so you may need to take 2 to 4 capsules to achieve the desired dosage.
The appropriate dosage of D-mannose depends on several factors such as age, health status, and other individual circumstances. Natural products aren’t always inherently safe, and dosage can be crucial. It’s important to follow the relevant instructions on the product label and consult a pharmacist, physician, or other healthcare professional before use   .