Variations in the Mineral Content of Bottled 'Still' Water Across Europe: Comparison of 182 Brands Across 10 Countries

Introduction: Kidney stone disease (KSD) is a highly prevalent disease worldwide. As water intake and its mineral content influence stone formation and recurrence, patients and physicians must be aware of the mineral content of drinkable water. We analyzed commercial bottled still water within Europe to assess the variation in its mineral composition across different manufacturers and countries. Materials and Methods: Data on the mineral composition of bottled still water regarding bicarbonate, calcium, magnesium, potassium, sodium, and sulfate concentration (mg/L) were collected from ten European countries. To collect the data, the two main supermarket chains in each participating country were either visited to check for the ingredient label on bottles or the online shop was consulted through the website of the supermarket in question. Descriptive statistics such as simple boxplots were used to illustrate the variation in mineral content. Results: One hundred eighty-two different commercial water brands were analyzed. Up to a fivefold variation in average concentrations per mineral between countries was observed. For calcium, a wide distribution was found in France and Switzerland compared with other countries with calcium levels ranging from 10.5 to 565 mg/L and 8.4 to 579 mg/L, respectively. By consuming 2 L of water with such high calcium levels, the daily reference intake for calcium is already achieved. Conclusions: The mineral content of bottled still water across Europe varies greatly. For patients with KSD it is important to be aware of the mineral content of the water they drink, as it might influence stone recurrence rates and necessitate alterations of their diet.