Magnesium – the role, absorption, and uptake in the body

  • Woman 19-30yrs 310mg/day; >30yrs 320mg/day
  • Men 19-30yrs 400mg/day; >30yrs 420mg/day

The majority of magnesium in the body occurs in the bones, muscles, and tissues.


  • Magnesium has many metabolic and structural functions it is required for the mitochondria to carry out oxidative phosphorylation.
  • It is involved in both aerobic & anaerobic energy generation plus glycolysis.
  • Maintenance of bone health & optimal bone growth.
  • Co-factor for more than 300 enzymes.
  • Plays a role in regulating potassium fluxes & the metabolism of calcium
  • Muscle & nervous system function.

Magnesium absorption

Magnesium is absorbed in the intestines by both active and passive processes. Kidneys play a central role in magnesium homeostasis through active reabsorption which is influenced by sodium load and the acid-base balance.

What affects magnesium uptake?

  • High fibre intakes of >40-50g per day lowers magnesium absorption
  • High zinc intakes ≥142mg per day reduces absorption
  • Protein intake <30g per day decreases magnesium absorption.
  • When Protein intake is exceptionally high renal magnesium excretion increases.
  • High dietary calcium intakes (~2600mg per day) combined with high sodium intake contributes to a shift to negative magnesium balance.

Deficiency/excess symptoms

  • Depletion of magnesium maybe observed mainly among athletes in endurance type sports.
  • Deficiency symptoms include muscle weakness, irritability, nausea, and depression.
  • In females: Sub-optimal intake of magnesium may cause or increase pre-menstrual tension and discomfort.
  • Excess: large intakes (3-5g) may have a laxative effect.
  • Individuals with abnormal renal function can be subject to hyper magnesium; symptoms include depression, nausea, vomiting & hypotension.

Supplement intake:

Magnesium in supplement form should be present with calcium in a 1 to 2 ratio of magnesium to calcium.

food sources include: 

Rice Bran – Oat Bran – Wheat Bran – Buckwheat Rye – Pumpkin seeds – Edamame Beans – Dates Kale – Banana – Spirulina – Quinoa – Brown Rice – Brazil Nut