A new report by Finnish health researchers says that drinking hard water actually can help people extend their lives by avoiding early death from cardiovascular disease.
"There are regional differences in the chemistry of the groundwater that correlate with the incidence of heart disease," Pekka Puska, director general of the Finnish National Health Institute, told AFP.
"The study shows that the softer the water is, the more heart disease there is," he added.
While researchers have been aware of this phenomenon for some time, most studies done so far have been very general, Puska said.
The new research is the first detailed survey, covering 19,000 incidents of heart attacks across Finland, and then linking them to geochemical data of the drinking water in the communities where the incidents had occurred.
Whether water is hard or soft depends on the quantity of mineral salts, typically magnesium, calcium, zinc, copper, aluminum, fluoride and iron, dissolved in it. Normally hard water is described as containing more than 250 parts per million of mineral salts, while mineral water typically has 500 parts per million.
Research from the west and south of Finland, where the drinking water is hard, found far fewer incidents of cardiovascular diseases than was the case in the north and east of the country, where the drinking water is soft, Puska said.
The authors of the study, which was published in the Journal of Epidemiology and Community Health said: "The large geographical variation and changes in the incident of heart attacks in Finland cannot be explained by individual lifestyle or genetic factors alone … Environmental exposures must also contribute to the development of the disease."
They added that common risk factors and socio-economic status provided only a partial explanation for higher heart disease risk in some areas, and further study is needed.