Alkaline water unlikely to prevent kidney stones, study finds

According to a recent study conducted by investigators at the University of California, Irvine (UCI), alkaline water contains scant levels of alkali, suggesting that products may have a negligible effect on urinary pH and urinary citrate levels and therefore may not offer any benefit for the prevention of recurrent kidney stones.^1,2

Roshan M. Patel, MD

"Our findings may help to guide the selection of other treatments, including beverages and over-the-counter products, for preventing recurrent urinary stones," said senior author Roshan M. Patel, MD, in the news release.² Patel is a urologist and vice chair of urology at UCI, as well as the director of the UCI Kidney Stone Center.

For the study, the investigators assessed 5 commercially available alkaline water brands: Essentia, Smart Water Alkaline, Great Value Hydrate Alkaline Water, Body Armor SportWater, and Perfect Hydration. Each product underwent anion chromatography and direct chemical measurements to determine their mineral contents. They were then compared with potassium citrate, the current gold standard for urinary alkalinization therapy that is frequently recommended to patients with uric acid and cystine urolithiasis, according to the authors.

Overall, data showed that pH levels for the alkaline water products ranged from 9.69 to 10.15. According to the news release, tap water typically has a pH level around 7.5.²

However, at a pH of 10, the alkaline water products would have a physiologic alkali content of 0.1 milliequivalent per liter (mEq/L), which the authors described as “trivial” compared with the typical metabolic acid production of humans of 40 mEq/L to 100 mEq/L per day. The alkali content was also deemed to be minimal when compared with potassium citrate.

Further, the 5 tested bottled alkaline waters contained no organic anions that could be metabolized to alkali aside from a small amount of citrate identified in the Body Armor product, although it was not included on the ingredient label. None of the other products met the detection threshold for citrate.

Patel explained in the news release, "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.”²

The investigators also assessed the mineral contents of other beverages and supplements that are commonly used to augment urinary citrate and/or the urine pH. They found that several products contained more alkali content than alkaline water and met the alkali recommendation levels of 30 mEq to 60 mEq per day with 3 or less servings set by the American Urological Association (AUA) and the European Association of Urology (EAU).

The product with the greatest potential alkali content was the synthetic supplement sodium bicarbonate (ie, household baking soda), with 17.4 mEq per quarter teaspoon. However, it also contained the highest sodium content at 400 mg per serving, which the authors say raises some concerns.

Another notable product was orange juice, which demonstrated an alkali content of up to 15 mEq/L per serving. Orange juice was also estimated to have the lowest cost per month required to meet the AUA/EAU target alkali concentration of 30 mEq per day.

However, the authors identified a key limitation of their study being that the products were not assessed when administered to uric acid or cystine stone-forming patients.

References

1. Piedras P, Cumpanas AD, McCormac A, et al. Alkaline water: Help or hype for uric acid and cystine urolithiasis? J Urol. 2024;211(2):276-284. doi:10.1097/JU.0000000000003767

2. Can drinking alkaline water help prevent kidney stones? Not likely, study finds. News release. Wolters Kluwer Health: Lippincott. January 10, 2024. Accessed January 11, 2024. https://www.newswise.com/articles/can-drinking-alkaline-water-help-prevent-kidney-stones-not-likely-study-finds