For those that are unable to read…I have pulled out the main ideas:
More than 50 studies in nine countries have been carried out on possible relationship of water hardness and health. Most of the investigations were in the United Kingdom, United States, and Canada; they reveal a consistent trend of significant statistical associations between the hardness characteristics of drinking water and the incidence of cardiovascular problems (heart disease, hypertension, and stroke) and, to a lesser extent, other diseases. Generally, reports have shown an inverse correlation between the incidence of cardiovascular disease and the amount of hardness of drinking water, or, conversely, a positive correlation with the degree of softness. Studies in the United States and Canada have shown that age-adjusted cardiovascular mortality rates among populations using very soft water may be as much as 15-20% higher than among populations using hard water. The differential reported for the United Kingdom may be as high as 40%.
Theories on Risk Factors
Several hypotheses have been offered on how components of drinking water may affect cardiovascular function and disease; these generally fall into one of the following classes:
1. That one or more of the principal "bulk" constituents of hardness in tap water are protective.
2. That one or more of the trace elements that tend to be present in hard water are protective.
3. That harmful metals are present in soft water, possibly having been picked up by leaching from the distribution system.
4. That other factors are involved. Each class of hypotheses is briefly reviewed below.
HARMFUL ELEMENTS IN SOFT WATER
Soft water tends to be more corrosive than hard water. As a result certain trace metals are found in higher concentrations in soft than in hard water. Several such metals have been suggested as possible intermediaries in the increased cardiovascular disease rates associated with soft water. Based on very limited data, cadmium, lead, copper, and zinc have been suspected to be possibly involved in the induction of cardiovascular disease. These metals often occur in plumbing materials and have been found to leach into soft drinking water.
Another possible variable is the different effect of hard and soft waters on the mineral composition of foods during cooking. It is theorized that soft water may remove a significantly higher proportion of various "protective" nutrients and elements from foods during cooking than do hard waters.