Magnesium is an essential dietary mineral, and the second most prevalent electrolyte in the human body. Magnesium deficiencies are common in developed countries. A deficiency increases blood pressure, reduces glucose tolerance and causes neural excitation.
Magnesium deficiencies are common in the western diet because grains are poor sources of magnesium. Other prominent sources of magnesium, like nuts and leafy vegetables, are not eaten as often. It is possible to fix a magnesium deficiency through dietary changes. If magnesium is supplemented to attenuate a deficiency, it acts as a sedative, reducing blood pressure and improving insulin sensitivity.
Maintaining healthy magnesium levels is also associated with a protective effect against depression and ADHD. Supplementation of magnesium is not very effective at reducing fat mass or cramps. Further evidence is needed to determine if magnesium supplementation can boost exercise performance, but initial results do not look promising.
The intestinal absorption of magnesium varies depending on how much magnesium the body needs, so there are not very many side-effects associated with supplementation. If there is too much magnesium, the body will only absorb as much as it needs. However, excessive doses may cause gastrointestinal distress and diarrhea.