Magnesium

Magnesium oxide itself is less soluble and may therefore also be less readily utilised by the body. However, in some supplements it is combined with citric acid, often in effervescent tablets, and once dissolved, magnesium citrate may form in the solution. This generally behaves more favourably in terms of solubility. [13] It is therefore always important to read the list of ingredients on the label.

Magnesium carbonate reacts with hydrochloric acid in the stomach to form magnesium chloride. [14] However, it does not make sense to assign a single fixed absorption percentage to a particular magnesium salt, as absorption varies considerably depending on the dose and the individual. Ultimately, magnesium is absorbed into the bloodstream as the Mg²⁺ ion. [3] The quantities of the so called carriers found in magnesium tablets, such as bisglycinate or malate, are not sufficient to produce the therapeutic effects sometimes described by manufacturers. For example, one study administered 3 g of glycine per day and observed a modest improvement in sleep. [15] Such an amount is unlikely to be found in magnesium tablets. Attempting to reach this level may also increase the risk of gastrointestinal problems, particularly diarrhoea. [1]