Magnesium (Mg) is one of the most important intracellular cations in the human body. It catalyzes many reactions of carbohydrate, protein and fat metabolism. Researches show that many people do not have enough products rich in magnesium in their diets. Proper/reference magnesium blood plasma level is 0.65–1.25 mmol/l. Magnesium deficiencies may cause arrhythmia as well as mood disorders, depression and difficulties in concentrating.

Magnesium deficiency in the human body is often recognized in the industrialized countries and is caused mainly by the increased consumption of the processed foods. Daily magnesium intake increases in stress, intense physical activity, pregnancy and lactation. Bioavailability of magnesium supplement depends on its chemical form, the presence of inorganic anion or organic ligand, water solubility, stability of the compound, presence of vitamin B₆ and potassium ions, daily dosage and administration. In this review bioavailability of organic and inorganic magnesium compounds, supplement composition and magnesium ion content is presented. Magnesium ion complexes with organic ligands are more stable in acidic environment, and give better absorption, thus higher bioavailability due to easier passage through the intestinal wall. Greater intestinal absorption of magnesium organic complexes, mainly citrates, than inorganic salts is observed.

Many clinical studies point to the importance of magnesium deficiencies in the development of hypertension and stroke. Magnesium has a direct, dilating influence on vascular endothelium through the influx of calcium into cells. In many studies it has been confirmed that there exists the dependence between the magnesium supplementation and the decrease in blood pressure. Antihypertensive efficacy of magnesium is small, therefore this cation can only be an additional element of a therapy. Magnesium decreases the risk of diabetes and metabolic syndrome development. Polish and European Society of Hypertension recommend the DASH diet, which contains 500 mg of Mg per 2100 kcal and which does not require additional Mg intake.