Which form of magnesium is best to take?

Organic forms of magnesium, such as magnesium citrate or magnesium glycinate, are absorbed better by the body than inorganic forms such as magnesium oxide. A systematic review of 14 comparative studies confirms this. The higher the dose, the smaller the proportion your body actually absorbs, so do not automatically take more than recommended.

For healthy people without a deficiency, the form matters less: all common forms are sufficient to maintain normal blood levels. Are you older, do you have type 2 diabetes, do you use antacids or certain blood-pressure patches (thiazide diuretics), or do you drink alcohol regularly? Then you are at greater risk of a deficiency and a well-absorbed, organic form is more meaningful.

Magnesium sprays, flakes and salt baths are popularly promoted, but there is no scientific evidence that magnesium is effectively absorbed through the skin. These claims have been heavily marketed but are not substantiated. If you want to supplement magnesium, simply opt for oral supplementation.

The picture regarding the effect of magnesium supplements on bone and muscle mass in older adults is mixed. A magnesium deficiency can negatively affect bone and muscle health, but whether supplementation actually reverses this has not been convincingly demonstrated. That does not mean your supplements are pointless, but do not expect a major bone-protective effect from them if your intake is otherwise sufficient.