We like high-magnesium Dunaliella salina algae, Mg taurate, Mg 2-AEP, Mg orotate, and Mg diglycinate, as well as Mg aspartate. These seem to be highly bioavailable and lowest in laxative effect. Magnesium oxide is the worst, with low to zero bioavailability, and a tendency to be readily converted to magnesium hydroxide (aka “Milk of Magnesia”) in the intestines.

Low magnesium can lead to muscle cramps, heart arrhythmias, hardening arteries, high blood pressure, and poor calcium utilization. Since it stimulates parathyroid hormone, the hormone that commands osteoclasts to tear down bone, supplemental Mg should be taken from morning to mid afternoon, when the pull of gravity counters parathyroid hormone by calling forth calcitonin, the hormone that stimulates bone building osteoblasts. Then, at night, when parathyroid hormone usually holds sway, take some calcium and vitamin D3 before retiring to reduce parathyroid hormone secretion.