Comparison of the mineral content of tap water and bottled waters

OBJECTIVES: Because of growing concern that constituents of drinking water may have adverse health effects, consumption of tap water in North America has decreased and consumption of bottled water has increased. Our objective s were to 1) determine whether North American tap water contains clinically important levels of calcium (Ca2+), magnesium (Mg2+), and sodium (Na+) and 2) determine whether differences in mineral content of tap water and comme rcially available bottled waters are clinically important. DESIGN: We obtained mineral analysis reports from municipal water authoriti es of 21 major North American cities. Mineral content of tap water was comp ared with published data regarding commercially available bottled waters an d with dietary reference intakes (DRIs). MEASUREMENTS AND MAIN RESULTS: Mineral levels varied among tap water source s in North America and among bottled waters. European bottled waters genera lly contained higher mineral levels than North American tap water sources a nd North American bottled waters. For half of the tap water sources we exam ined, adults may fulfill between 8% and 16% of their Ca2+ DRI and between 6 % and 31% of their Mg2+ DRI by drinking 2 liters per day. One liter of most moderate mineralization European bottled waters contained between 20% and 58% of the Ca2+ DRI and between 16% and 41% of the Mg2+ DRI in adults. High mineralization bottled waters often contained up to half of the maximum re commended daily intake of Na+. CONCLUSION: Drinking water sources available to North Americans may contain high levels of Ca2+, Mg2+, and Na+ and may provide clinically important po rtions of the recommended dietary intake of these minerals. Physicians shou ld encourage patients to check the mineral content of their drinking water, whether tap or bottled, and choose water most appropriate for their needs.