Magnesium - what you need to know

Jacob Strøm

Jacob Strøm

Performance specialist. Cand.scient. Sports Science. 25+ certificates from EXOS, Barca Innovation Hub etc.

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Magnesium is an essential mineral and the second most prominent electrolyte in our body and is involved in over 300 enzymatic processes, including energy (ATP) production.
Magnesium - worth knowing - Football performance

Magnesium deficiency has become common in the Western world, which can lead to increased blood pressure, decreased glucose tolerance and can lead to neural 'overstimulation'.

We've probably all heard that we should take magnesium (especially in the form of ZMA), but never really with a documented justification of why, how much and what form is best to take.

And is magnesium really a 'sleeping pill'?

In this guide you will find answers to all these questions and get more out of your supplements.

Magnesium deficiency is often seen in the Western world because cereals (of which many eat a lot) are a poor source of magnesium. While other hugely good sources of magnesium, such as nuts and green vegetables, are not eaten as often or in as large quantities.

So you can easily cover your magnesium needs with a better diet based on more vegetables. Eating more vegetables or taking more magnesium will help lower blood pressure and improve insulin sensitivity.

Magnesium sources - Football performance

How much magnesium do we need?

The Danish Health Authority recommends that women and men get 280 and 350 mg per day respectively (1), while recommendations in the US are slightly higher at 310-420 mg per day (2). Based on these figures, about 68% of the adult population in the US consumes 19% less magnesium than recommended (3).

Can you get too much magnesium?

The absorption of magnesium depends largely on how much the body needs, and there are few side effects from taking too much magnesium. If the intake is too high, the body will simply absorb what it needs and dispose of the rest. However, excessive doses can lead to diarrhea, which also depends largely on the form you take (more on this later).

Magnesium and sleep - how are they linked?

This suggests that magnesium plays a role when it comes to sleep, as magnesium intake can have a calming effect. Magnesium is significantly but weakly correlated with sleep depth independent of dietary energy composition, with the quartile with the least magnesium also having similar results with sleep (4). This is probably more than effect rather than cause, as deliberate sleep deprivation (80% of normal sleep volume) for 4 weeks has been shown to reduce magnesium levels in red blood cells by 3.5% (5). This means that lack of sleep alone may be causing you to have insufficient magnesium.

In a study of 12 healthy elderly subjects, increasing magnesium intake (10 mmol and 30 mmol at the end) for 20 days led to a 63.3% increase in deep sleep and decreased cortisol (stress hormone) levels during sleep, which counteracted age-related changes in sleep patterns (6).

Similar results were also found in people aged 59 +/- 8 years who consumed less magnesium than recommended. Over 7 weeks, they received 320 mg magnesium citrate daily, which improved their sleep quality and some inflammatory parameters. An interesting finding was also that no increase in serum (liquid blood) magnesium was found compared to the placebo group, except for those subjects who were already deficient (7).

Does taking ZMA give you strange dreams?

ZMA is a popular product, and is a mixture of Zinc, Magnesium and Vitamin B6 (pyridoxine), and many people say they get strange dreams from taking it.

This has not been adequately studied, but a pilot study (8) suggests that a dose of 250 mg pyridoxine may alter the experience of dreams in young men. This is thought to be due to an increased conversion of tryptophan to serotonin. However, this dose of vitamin B6 is rarely found in ZMA products, which are usually around 10-50 mg B6.

One study found a synergy between B6 and magnesium to reduce anxiety in women with PMS (9). Theoretically, therefore, it may be that the composition of ZMA leads to an increased utilization of B6, and therefore may cause strange dreams. However, it is worth stressing that there is nothing magical about this composition of zinc, magnesium and vitamin B6.

Bodylab - ZMA

Borrowed image from Bodylab - not a recommendation to use their ZMA over others (Photo: Bodylab)

What kind of magnesium should I take?

Magnesium in pills is bound to another molecule, typically a salt, to stabilize magnesium and prevent a reaction with other minerals.

In the following section, I will review the different forms and conclude with concrete recommendations on which form to take and which one you should definitely not waste your money on.

Magnesium Oxide
Magnesium oxide has an extremely low bioavailability in the body of about 4-5% (10), which means that you cannot absorb more than 4-5% of the total amount of magnesium.

Due to its low absorption and low weight, magnesium oxide is typically used as a filler in many other products.

A higher intake (1 g per day) of magnesium oxide can lead to diarrhoea (15)

Magnesium Citrate
Magnesium citrate is one of the most widely used in supplementation, due to its high water solubility. Magnesium bound to citrate appears to have a higher bioavailability of about 25-30% (many tables say 90%, but it has not been possible to find sources here) (11,12).

Magnesium Aspartate
Magnesium bound to the amino acid L-Aspartate has been shown to have a higher bioavailability than oxide (13), but less than citrate (11).

Magnesium DiGlycinate
Magnesium DiGlycinate has a higher bioavailability than oxide, and is absorbed in other areas of the stomach, compared to other magnesium supplements (14). Magnesium BisGlycinate is a more popular and available form on the market, and will have close to equal bioavailability.

Choose these forms of magnesium:

When it comes to magnesium, it can be beneficial to choose different types of magnesium and possibly spread them out over the day.

Oxide I would definitely not recommend due to the very low absorbency, which can lead to diarrhea. Instead, I would recommend citrate and bis- or di-glycinate. Other forms such as citramate, gluconate and taurinate also seem to have good absorbency.

How much and when should I take magnesium?

I recommend a daily dose of 300 - 600 mg depending on your needs and based on your diet and any symptoms.

As magnesium has a calming effect I would recommend that you take it before bed, along with your last meal/shake/smoothie.

The daily dose can also be divided during the day, for example 200 mg with breakfast and 400 mg before bedtime.

It can also be taken after exercise to help recovery, however be aware that magnesium should not be taken on an empty stomach...


  3. Jacka FN, et al. Association between magnesium intake and depression and anxiety in community-dwelling adults: the Hordaland Health Study. Aust N Z J Psychiatry(2009).
  4. Sato-Mito N, et al. The midpoint of sleep is associated with dietary intake and dietary behavior among young Japanese women. Sleep Med.(2011)
  5. Takase B, et al. Effect of chronic stress and sleep deprivation on both flow-mediated dilation in the brachial artery and the intracellular magnesium level in humans. Clin Cardiol(2004).
  6. Held K, et al.Oral Mg(2+) supplementation reverses age-related neuroendocrine and sleep EEG changes in humans. Pharmacopsychiatry(2002).
  7. Nielsen FH, Johnson LK, Zeng H. Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep. Magnes Res(2010)
  8. Ebben M, Lequerica A, Spielman A. Effects of pyridoxine on dreaming: a preliminary study . Percept Mot Skills. (2002)
  9. De Souza MC, et al. A synergistic effect of a daily supplement for 1 month of 200 mg magnesium plus 50 mg vitamin B6 for the relief of anxiety-related premenstrual symptoms: a randomized, double-blind, crossover study . J Womens Health Gend Based Med.(2000)
  10. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. (2001)
  11. Lindberg JS, et al. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr(1990).
  12. Walker AF, et al. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res(2003)
  13. Mühlbauer B, et al. Magnesium-L-aspartate-HCl and magnesium-oxide: bioavailability in healthy volunteers. Eur J Clin Pharmacol(1991).
  14. Schuette SA, Lashner BA, Janghorbani M. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection.JPEN J Parenter Enteral Nutr(1994).
  15. de Lordes Lima M, et al. The effect of magnesium supplementation in increasing doses on the control of type 2 diabetes.Diabetes Care. (1998)

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