Although drinking water, with some rare exceptions, is not the major source of essential elements for humans, its contribution may be important for several reasons. The modern diet of many people may not be an adequate source of minerals and microelements. In the case of borderline deficiency of a given element, even the relatively low intake of the element with drinking water may play a relevant protective role. This is because the elements are usually present in water as free ions and therefore, are more readily absorbed from water compared to food where they are mostly bound to other substances.
Animal studies are also illustrative of the significance of micro quantities of some elements present in water. For instance, Kondratyuk (35) reported that a variation in the intake of microelements was associated with up to six-fold differences in their content in muscular tissue. These results were found in a 6-month experiment in which rats were randomized into 4 groups and given: a.) tap water, b.) low-mineral water, c.) low-mineral water supplemented with iodide, cobalt, copper, manganese, molybdenum, Zinc and fluoride in tap water, d.) low-mineral water supplemented with same elements but at ten times higher concentrations. Furthermore, a negative effect on the blood formation process was found to be associated with non-supplemented demineralized water. The mean hemoglobin content of red blood cells was as much as 19% lower in the animals is that received non-supplemented demineralized water compared to that in animals given tap water. The hemoglobin differences were even greater when compared with the animals given the mineral supplemented waters.
Recent epidemiological studies of an ecologic design Russian populations supplied with water varying in TDS suggest that low-mineral drinking water may be a risk factor for hypertension and coronary heart disease, gastric and duodenal ulcers, chronic gastritis, goiter, pregnancy complications and several complications in newborns and infants, including jaundice, anemia, fractures and growth desorders. However, it is not clear whether the effects observed in these studies are due to the low content of calcium and magnesium or other essential elements, or due to other factors.
Lutai conducted a large cohort epidemiological study in the Ust-Ilim region of Russia. The study focused on morbidity and physical development in adults, children and pregnant women and their newborns in two areas supplied with water different in TDS. One of these area was supplied with water lower in minerals (mean values: TDS 134 mg/L, calcium 18.7 mg/L, magnesium 4.9 mg/L, bicarbonates 86.4 mg/L) and the other was supplied with water higher in minerals (mean values:TDS 385 mg/L, calcium 29.5 mg/L, magnesium 8.3 mg/L, bicarbonates 243.7 mg/L). Water levels of sulfate, chloride, sodium, potassium, copper, Zince, manganese and molybdenum were also determined. Area therespetive areas. Populations of the two areas did not differ from each other in eating habits, air quality, social conditions and time of residence in the respective areas. The population of the area supplied with water lower in minerals showed higher incidence rates of goiter, hypertension, ischemic heart disease, gas tic and duodenal ulcers, chronic gastritis, cholecystitis and nephritis. Children living in this area exhibited slower physical development and more growth abnormalities, pregnant women suffered more frequently from edema and anemia. Newborns of this area showed higher morbidity. The lowest morbidity was associated with having calcium levels of 30-9- mg/L, magnesium levels of 17-35 mg/L, and water could be considered as physiologically optimum.