D-mannose is a bioactive monosaccharide found in foods and frequently recommended to prevent recurrent urinary tract infections (RUTIs) in women. It is unknown if this protective effect against RUTIs results from urinary pH changes. D-Mannose has been effective in inhibition of bacterial colonization of the bladder wall for the prevention of UTIs [1]. Mannose in the body can be converted to glucose and contributes to the synthesis of glycoproteins. Increased consumption of glucose has been shown to decrease urine pH [2]. We therefore hypothesized that individuals who consume more D-mannose in their diet would also have lower urinary pH. Our goal was to study the effect of D-mannose on urinary pH by analyzing the D-mannose content consumed in foods and supplements reported in a diet diary of women with a history of RUTIs, comparing this dietary intake with concurrent urinary pH measurements.

Following a published, prospective, IRB-approved study on urine pH and diet of women with RUTIs [2], we reviewed the urine pH and D-mannose content of foods and beverages reported in diet diaries over 3- to 7-consecutive days. During the study, menopausal women with a history of recurrent urinary tract infections were given urinalysis reagent strips to record their urine pH four times per day. They concurrently completed a food diary, recording all food and beverage intake during that measurement period. Food diaries were then analyzed using the Nutritionist Pro analysis software to determine the daily consumption of 118 micro and macronutrients of each participant. Three groups were identified based on urine pH: those with persistently low pH under 6 (group 1), persistently high pH always above 6 (group 2), and variable pH (group 3). 
Specific amount of D- Mannose or Mannose in food sources is not provided in nutritional analysis; therefore, we categorized foods based on D-mannose content reported in a previous study [3]. The total amount of D-mannose consumed was calculated by adding together the total weight of each D-mannose-containing food consumed for each participant at each meal. Total D-mannose consumed (naturally and vitamin and mineral supplements) between groups was compared using a mixed model analysis, with a compound symmetric covariance structure to account for meals from the same patient. Overall distribution of weight of foods in grams containing D-mannose were visualized using box and whisker plots.

Over the study period, 22 women supplied urine pH and diet data, from whom 129 breakfasts, 125 lunches, and 128 dinners were studied. No difference was found in the amount of D-Mannose foods consumed between the three urine pH groups. We observed that D-mannose foods were most often consumed at breakfast, with median amounts ranging from 141.6 g to 162.3 g for group 2 and group 1, respectively. For this reason, a representative graph for breakfast of the weight of foods containing D-mannose by group is displayed in Figure 1.

D-mannose supplementation is frequently encouraged in the management of RUTIs with dosages ranging from 500 to 3,000 grams; however, diet can also supply D-mannose naturally. We found that the amount of D-mannose consumed in foods and supplements did not differ significantly among women with persistently low, high, or variable urinary pH.

        	In foods, mannose is a complex carbohydrate and has been found in coffee, eggs, fruits (mango, peaches, apples, oranges, blueberries, black currants, cranberries), legumes and soybeans, vegetables (cabbage, turnips, and tomatoes) and guar gums, fenugreek gum, and konjac gums, ivory nuts, aloe vera and bakers’ yeast. Commercially, mannose powders, because of their thickness, have been used to improve texture in ice cream, salad dressings and processed fruits. A previous study that analyzed the effect of dietary nutrients on urine pH found an association between total dietary sugar and lower urine pH [3]. Since mannose is metabolically converted from glucose, identifying intake from carbohydrates and other mono- and polysaccarides would provide some insight whether these nutrients, specifically a carbohydrate/glucose source, affects urinary D- Mannose levels. Identification of dietary sources of D-mannose; therefore, may offer another mechanism by which UTIs can be prevented.

	Strengths of this study include the robust nutrient analysis performed based on food diaries and the number and consistency of urine pH measurements obtained by each participant. Limitations of this study include the number of participants who were recruited from a single tertiary care center. In addition, in this analysis we were only able to classify foods as containing D-mannose (yes or no), with the amount consumed determined by the weight of D-mannose-containing foods. In future studies, it would be beneficial to calculate the relative amounts of D-mannose in each food/beverage and multiply that variable by the weight of the food consumed in order to obtain a more accurate measurement.

We found that the amount of D-mannose consumed in foods and supplements did not differ significantly among women with persistently low, high, or variable urinary pH. We continue to investigate other food sources and dietary patterns such as  prebiotics, probiotics,  acidic and alkaline intake and specific food categories as may be related to influencing urine pH.

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Chavez JA, Chavez JM, Kuprasertkul A, Carroll TF, Fuentes JL, Christie AL, Alhalabi F, Zimmern PE. Prospective Evaluation of Daily and Weekly Urine pH Variations Along With Diet Intake in Postmenopausal Women With Recurrent Urinary Tract Infections. Female Pelvic Med Reconstr Surg. 2021 Feb 1;27(2):e352-e359. doi: 10.1097/SPV.0000000000000931. PMID: 33009261.
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