Magnesium is also crucial in the production of energy as it is a part of the Mg-ATPase complex and is essential for oxidative phosphorylation. Magnesium is an essential element required by the body as it takes part in over 300 enzymatic reactions and is necessary for the biochemical functioning of numerous metabolic pathways such as protein synthesis, muscle contraction, blood glucose control, blood pressure regulation and nerve function. Magnesium homeostasis is largely controlled by the kidneys. In cases of lower magnesium levels, more is absorbed in the gut and, when you have higher magnesium levels, less is absorbed. Intestinal absorption is not directly proportional to magnesium intake but is dependent mainly on your magnesium status.
Of the total dietary magnesium consumed, only about 24–76% is absorbed in the gut and the rest is eliminated in the faeces, as explained in this paper on Magnesium Basics. Magnesium is mostly absorbed in the small intestine and is dependent on the amount ingested. The blood (serum) contains only 1% Magnesium. In the body, approximately 60% of magnesium is stored in bones and 25% in muscle.
It occurs as the free cation, a positively charged ion, Mg2+ in aqueous solutions or as the mineral part of compounds, including chlorides, carbonates and hydroxides. Magnesium is an alkaline earth metal and the fourth most common mineral in the human body.