Does Hard Water Cause Kidney Stones?

Insufficient intake of water and other liquids, i.e. permanent dehydration, even if slight, surely increases the risk for urolithiasis of all types. Urolithiasis is the formation of urinary calculi or stones in the bladder or urinary tract. On the other hand, qualitative assessment shows that the content of water minerals, more precisely of magnesium and calcium, plays a less important role. Urinary stone formation is a process involving multiple factors, i.e. not only intake of liquids, but also genetic predisposition, eating habits, climatic and social conditions, gender, etc.

Several studies documented that higher water hardness is associated with higher incidence of urolithiasis among the population supplied with such water. However, more studies found softer water to be associated with a higher risk for urolithiasis. Nevertheless, most recent epidemiological studies explain these controversial results by differences in the study designs and say that water hardness ranging between the values commonly reported for drinking water is not a significant factor in urolithiasis (Singh et al, 1993; Ripa et al, 1995; Kohri et al, 1993; Kohri et al, 1989).

Any correlation between water hardness, or the drinking water calcium or 14 magnesium level, and the incidence of urolithiasis was not found in the last vast USA epidemiological study with 3270 patients (Schwartz et al, 2002). The quoted Japanese studies did not find that the water calcium or magnesium levels alone had an effect on the incidence of urolithiasis but did find that the Mg to Ca ratio had: one study reported the lower Mg to Ca ratio to be associated with a higher risk for urolithiasis regardless of type and the incidence of urolithiasis to correlate with the type of geological subsoil. (Kohri et al, 1989) Another study found a correlation between the higher Mg to Ca ratio and higher incidence of infectious phosphate urolithiasis (Kohri et al, 1993).

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