Despite the essential nature of magnesium there is no specific food that provides a high amount of magnesium. Good sources of magnesium include whole grains, spinach, nuts, legumes and potatoes. However, even with the wide availability of magnesium in foods, at least 60% and possibly as much as 80% of adults do not consume the Recommended Dietary Intake (RDI) for magnesium (310-420mg/day). In addition, absorption of magnesium from the small intestine decreases and excretion by the kidneys increases as we age. Symptoms of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue and weakness. Due to the difficulty in reaching the RDI for magnesium from food sources alone, supplements are increasing being used. The quality of the magnesium depends not only on its source, the magnesium content of the supplement, but also on its bioavailability – that is the ability of magnesium to be absorbed and utilised by the body. As shown in the figure below magnesium oxide traditionally has the highest magnesium content at 60% but also the lowest solubility while at the other end of the table below magnesium chloride and magnesium sulphate have the highest solubility but the lowest levels of magnesium. Magnesium hydroxide is the perfect balance possessing a high level of magnesium and a 50% higher solubility than magnesium oxide in water (.009g/L vs .006g/L). Furthermore, it is soluble in stomach acid allowing absorption into the blood stream. Indeed, magnesium oxide must convert to magnesium hydroxide before dissolution in acid can begin.