17 Oct Magnesium – the role, absorption, and uptake in the body
Recommended Daily Intake (RDI):
- 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 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.
- 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.
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