MAGNESIUM IN DRINKING-WATER AND BODY MAGNESIUM STATUS MEASURED USING AN ORAL LOADING TEST

Epidemiological studies have shown an inverse relationship between mag nesium in drinking water and death from ischaemic heart disease. The q uestion is whether magnesium in drinking water can be critical for the body magnesium status. The aim of this study was to investigate, usin g an oral loading test, whether a change in body magnesium status coul d be found among people who change from drinking water with a low magn esium concentration to water with higher concentrations. The subjects participating in the study were 9 men and 3 women 65 - 70 years old, l iving in the city of Goteborg, Sweden, where the magnesium concentrati on in the tap water is low (1.6 mg/l). Drinking water was prepared wit h 200 mg MgCl2.6H(2)O added per litre to a level of 25 mg/l, and was d istributed to the subjects twice a week for 6 weeks. Excretion of magn esium, potassium and creatinine, basal and after oral magnesium loadin g (tablets containing 575 mg), was measured in 24 h urine before and a fter the supplementation period. Calculations were made for the total excretion (mmol/24 h), and in relation to creatinine. The subjects' in take of magnesium via food and water was estimated using a questionnai re. There was a difference between the post load excretion of magnesiu m, expressed as the magnesium/creatinine ratio, before and after the s upplementation period. The mean percentage change was a 14.6% (p = 0.0 47) increase. No changes were found for potassium. In summary, the res ults indicate that magnesium in drinking water can affect body magnesi um status.