Mineral content variations between Australian tap and bottled water in the context of urolithiasis.

Objectives: The objective of this study is to investigate the variations in mineral content of tap drinking water across major Australian cities, compared with bottled still and sparkling water, and discuss the possible implications on kidney stone disease (KSD). Materials and Methods: The mineral composition of public tap water from 10 metropolitan and regional Australian cities was compared using the drinking water quality reports published from 2019 to 2021 by the respective water service utilities providers. Specifically, average levels of calcium, bicarbonate, magnesium, sodium, potassium, and sulphates were compared with published mineral content data from bottled still and sparkling drinking water in Australia. Results: The median or mean (depending on report output) mineral composition was highly variable for calcium (range 1.3 to 20.33 mg/L), magnesium (range 1.1 to 11.2 mg/L), bicarbonate (range 12 to 79 mg/L), sodium (range 3 to 47.1 mg/L), potassium (range 0.4 to 3.23 mg/L) and (sulphates range <1 to 37.4 mg/L). Calcium, magnesium and bicarbonate levels in tap water were lower than in bottled sparkling water. Consumption of 3 L/day of the most calcium rich tap water would fulfil 4.7% of the RDI, compared with 8.7% with bottled sparkling water. Consumption of 3 L of the most magnesium rich tap water would fulfil 8% of the RDI, compared with 13.6% with bottled sparkling water. Conclusion: The mineral content of tap drinking water varied substantially across major Australian city centres. Bottled sparkling water on average provided higher levels of calcium, bicarbonate and magnesium and may be preferred for prevention of calcium oxalate stones. These findings may assist counselling of patients with KSD depending on geographic location in the context of other modifiable risk factors and 24-h urine analysis results.