Magnesium-deficient rats prefer magnesium-containing to pure water, but not to sweet tasting solutions

Groups of 3 x 20 female Sprague Dawley rats weighing 80-140 g were kept on a Mg-deficient diet (135 ppm Mg) during 14 days. Starting on the 9th day, 4 animals per cage were offered 3 drinking-bottles in a randomized order, containing either pure water, or water with 16 mmol Mg/1, respectively with 5 mmol saccharin/1(triangle test). One subgroup received 10 mmol Mg/kg body weight twice daily by gavage. Additional animals were fed a standard laboratory chow. Saccharin increased total fluid consumption; sweet fluid was clearly preferred to Mg-containing or to pure water. On the other hand, Mg-containing water was preferred to pure water; hypomagnesemia was significantly attenuated by water-borne Mg. Weight loss of 14% and loss of appetite caused by Mg deficiency were not fully compensated during the 5-day treatment period. Since Mg-sufficient rats did not prefer Mg-rich water in contrast to sweet solutions, these data allow to conclude that the preference for Mg has to develop during Mg deficiency.