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Results suggested bottled alkaline water had no added benefit over tap water for providing alkali content and alkalinizing urine pH.
Although increased pH is a major selling point of most commercially available alkaline water, anion chromatography and direct chemical measurements of 5 popular brands revealed trace amounts of minerals and organic anions resulting in negligible alkali content and thus a presumed minimal impact on urinary pH and urinary citrate levels.
The alkaline content of Essentia, Smart Water Alkaline, Great Value Hydrate Alkaline Water, Body Armor SportWater, and Perfect Hydration was compared to that of other beverages and supplements, with results suggesting each examined alkaline water provided no added benefit over tap water for providing alkali content and alkalinizing urine pH in patients with uric acid and cystine urolithiasis.1
"While alkaline water products have a higher pH than regular water, they have a negligible alkali content – which suggests that they can't raise urine pH enough to affect the development of kidney and other urinary stones," Roshan Patel, MD, chief of the division of endourology and director of the Kidney Stone Center at the University of California Irvine, explained in a press release.2
A urinary alkalizer, potassium citrate is often prescribed to patients with uric acid and cystine stone urolithiasis to raise their urine pH. Adherence to potassium citrate tablet therapy poses a challenge for many patients due to the burden of pills, its cost, and the associated side effects. Alkaline water has been proposed as an alternative approach for raising urinary pH, but information about its use for uric acid and cystine urolithiasis in humans is limited.1,3
To assess the potential use of commercially produced alkaline water for alkalinizing urine pH, Patel and a group of investigators tested a bottle from each brand of alkaline water twice over the span of a week, measuring the pH of each beverage using a pH electrode and measuring citrate and bicarbonate using ion chromatography.1
Using the PubMed and Scopus databases, investigators performed a comprehensive literature review using relevant keywords and phrases to examine the previously determined alkali content of various beverages and supplements promoted for reducing the risk of lithogenesis. These values were compared to the tested samples of bottled alkaline water.1
Investigators noted the pH of the 5 brands of alkaline water was similar, falling within a narrow range of 10. Body Armor SportWater had the highest pH at 10.15 and Smart Water Alkaline had the lowest pH at 9.69.1
Electrolyte and physiologic alkali content were minimal across all examined brands, none of which tested above the detection threshold for citrate. Due to their trace amounts of minerals and organic anions, the alkali load of the tested alkaline waters was limited to that provided as hydroxyl ions. In contrast, investigators pointed out several of the reviewed alternative beverages and supplements contained the recommended daily alkali content of 30-60 mEq in 2-3 servings.1
Among the alkali-containing beverages and supplements examined, sodium bicarbonate was found to provide the greatest amount of alkali, 17.4 mEq per serving, at the lowest cost, albeit with a mild increase in dietary sodium load (400 mg per serving).1
Although there seemed to be no discernible advantage in terms of increasing alkali content, investigators suggested the increased palatability of alkaline waters could lead to greater fluid intake, which has proven advantageous for those at risk of developing kidney stones. However, this was purely speculative as it was not within the scope of the present study.1
“Our findings may help to guide the selection of other treatments, including beverages and over-the-counter products, for preventing recurrent urinary stones," Patel concluded.2