Health Aspects of Calcium and Magnesium in Drinking Water
The symposium presented a wide range of perspectives regarding the question of the value of providing drinking water with a small amount of magnesium and/or calcium. The symposium was not designed to reach a conclusion; that will be a function of subsequent WHO Expert Committee and Guidelines activities. It is clear that large portions of the world's population are deficient in daily magnesium and calcium intake relative to recommended values and the intake seems to decrease further with age.
Water treatment processes can readily add minerals at low cost, and softening processes in the central treatment plant and the home can be adjusted to obtain desirable levels of magnesium and calcium in the drinking water. Water manufactured by desalination or reuse should be remineralized prior to entry into the water distribution system to increase alkalinity and control its corrosivity toward piping. Remineralization methods that include addition of calcium and magnesium are more desirable than other techniques because they also contribute nutrient minerals to water that will be consumed or used in food preparation.
There are several ways to improve the total intake of nutrient minerals that are not mutually exclusive. The selection is a matter of success potential, cost, widespread impact across the population, public health policy and law. The preferable approach is probably via improved diet e.g. by greater consumption of vegetables and dairy products.
Some bottled water and beverages can be fortified to provide supplemental nutrients. This is a particularly efficient approach since bottled water is growing in popularity in many areas, all of the water is consumed, and the incremental unit costs are negligible.
In general, a combination of these approaches tailored to each society would probably achieve the most success. The public needs to know what they are consuming so that they can make informed choices, but care must be exercised to protect against excessive calcium and magnesium consumption for some individuals and in some circumstances.
Magnesium in drinking water and body magnesium status measured using an oral loading test.
Epidemiological studies have shown an inverse relationship between magnesium in drinking water and death from ischaemic heart disease. The question is whether magnesium in drinking water can be critical for the body magnesium status. The aim of this study was to investigate, using an oral loading test, whether a change in body magnesium status could be found among people who change from drinking water with a low magnesium concentration to water with higher concentrations. The subjects participating in the study were 9 men and 3 women 65-70 years old, living in the city of Göteborg, Sweden, where the magnesium concentration in the tap water is low (1.6 mg/l). Drinking water was prepared with 200 mg MgCl2 x 6H2O added per litre to a level of 25 mg/l, and was distributed to the subjects twice a week for 6 weeks. Excretion of magnesium, potassium and creatinine, basal and after oral magnesium loading (tablets containing 575 mg), was measured in 24 h urine before and after the supplementation period. Calculations were made for the total excretion (mmol/24 h), and in relation to creatinine. The subjects' intake of magnesium via food and water was estimated using a questionnaire. There was a difference between the post load excretion of magnesium, expressed as the magnesium/creatinine ratio, before and after the supplementation period. The mean percentage change was a 14.6% (p=0.047) increase. No changes were found for potassium. In summary, the results indicate that magnesium in drinking water can affect body magnesium status.
Rubenowitz E, Axelsson G, Rylander R.