What is magnesium, and what does it do?

Magnesium is a mineral the body holds mostly in bone, and six nutrient function statements for magnesium are recognised in the annex.

What does magnesium do?

The annex to Thai Ministry of Public Health Notification No. 447 (B.E. 2566) recognises several statements:

• Magnesium is a component of bones and teeth
• Magnesium contributes to the normal function of the muscle and nervous system
• Magnesium contributes to electrolyte balance
• Magnesium contributes to normal energy-yielding metabolism
• Magnesium contributes to normal protein synthesis
• Magnesium contributes to the maintenance of normal bones and teeth

Where is it in the body?

About half is held in bone. Most of the rest is in muscle and other tissue, and under one per cent is in blood. That is why a blood figure does not directly reflect the total amount in the body.

Where does it come from in food?

Nuts and seeds, pumpkin seeds and almonds in particular; dried beans; wholegrains; dark leafy greens; and dark chocolate.

Refining grains removes a lot of it, which is why brown rice supplies more magnesium than white.

How much per day?

Recommended intakes set by the US National Academies' Food and Nutrition Board, as published by the NIH Office of Dietary Supplements, for adults range from roughly 310 to 420 mg a day depending on sex and age.

There is a separate upper limit of 350 mg a day that applies specifically to supplemental magnesium, not to magnesium obtained from food.

How do the forms differ?

Oxide, citrate and bisglycinate are the ones seen most often. Each carries a different proportion of magnesium per unit weight of compound, and they differ in how readily they dissolve.

Labels usually state the elemental amount, as in "each tablet provides magnesium X mg". That figure is the one to compare, not the weight of the compound.

When should it be taken?

There is no fixed time. Some people find it sits better with food. Large amounts of magnesium can interfere with calcium and iron absorption, so separating them in time is easier than taking everything at once.

If you take prescription medication or have any kidney problem, speak to a doctor before supplementing.

Dietary supplements are not intended to prevent, treat or cure any disease.