In the late 1950s, Kobayashi in East Asia  and in the early 1960s Schroeder in the United States  called attention to a previously unsuspected and still unexplained inverse relationship between cardiovascular disease and 'hardness' of drinking water. The effect has been reported from many areas and by many investigators [5,6]. Negative reports have generally considered relatively small and possibly overlapping areas, or areas with little difference between the hardness of the water supplies which were compared. Thus, the effect seems to be real , but the mechanism is unknown. It has been suggested that hard water contains a protective trace substance or that soft water contains a toxic one [4-6]. In addition to attempts to implicate the major contributors to water hardness, calcium and to a lesser extent magnesium, various trace elements have been suggested as causes for this effect, primarily as possible toxic substances. The characteristics of water generally correlate with its geochemical environment, and a number of studies have also shown the relationship of cardiovascular pathology to geochemical environment. As early as 1958, Tromp in the Netherlands found the mortality rates for arteriosclerotic heart disease to be highest in those areas which were underlain by sea-clay soils and peat soils, while lower rates prevailed on sandy soils of glacial origin. The former soils were considered to be generally deficient in trace elements . Masironi hypothesizes that the geographic differences in cardiovascular disease are often evident in areas which are underlain with soils which are poor in essential trace elements and that this is confirmed by the degree of mineralization of local water, manifesting itself in the water supply . Again, many investigators have published studies which demonstrate an increase in death rates related to geologic conditions [8-11]. Selenium concentration in plants has also long been considered a possible cause for the inverse association with death rates from hypertensive heart disease and coronary heart disease. Numerous observations have been made in more than 25 countries, and selenium blood levels have been noted to be inversely associated with death rates from coronary heart disease in the United States [12,13]. The subject has recently been extensively reviewed by Lockitch .
|Number of pages||20|
|Journal||Journal of Trace Elements in Experimental Medicine|
|State||Published - Sep 12 1991|