But what about the removal of hardness?
Some epidemiological studies carried out over the last 50 years have indicated that people living in areas where the water supply was naturally soft are slightly more prone to cardiovascular disease (heart attacks) than those living in areas with a hard water supply. When the studies have then focused on specific components of the water such as calcium, the correlation disappeared. However, people began to extend the theory from naturally soft water to softened water and this has led to the precautionary conclusion that it is preferable to drink the unsoftened, hard water.
However, tests then conducted in some cities where the water supply was softened by the water supplier did not support the correlation.
In November 2003 the World Health Organisation held a consultation on the issue of nutrition and drinking water, which considered the new data on hardness and cardiovascular disease. The group also requested advice relating to home water softening devices in relation to the advisability of retaining a source of water containing calcium and magnesium.
The World Health Organisation currently states that “..the available data are inadequate to permit a conclusion that the association is causal. No health based guideline value is proposed for hardness.” The Drinking Water Regulations do not include a specification for a minimum level of hardness.