@k09 If a person's kidneys are working properly, a person will excrete all the excess elements he/she doesn't need in the urine. Diseased/disordered kidneys will have problems. Before taking large amounts of elemental supplements, one should have a blood assay to determine kidney function. Then, there's also dietary problems: people often don't get enough magnesium in their diets due to the quality of the soils in which their produce, if they eat any regularly, is grown. So, I can see why one physician might caution against willy-nilly, seat-of-the-pants, guesstimated supplementation. Others might say go ahead...can't hurt. That would be incautious to me.