Magnesium is a vitally important mineral for our health. It is involved in over 300 enzyme reactions in the body, which means it plays a role in hundreds of different processes that keep us alive. It is needed for energy production, muscle and nerve function, and for our bones and teeth (about half the body’s magnesium is stored in the bones). Our best sources of magnesium are whole plant foods, such as seeds, nuts, beans and pulses, and green leafy vegetables.
Primary functions of Magnesium
- Magnesium is essential for nerve and muscle function. Like calcium, it is an electrolyte – a mineral that keep us hydrated and allows nerve signals to travel around the body, including to and from the muscles. About a quarter of the body’s magnesium is found in the muscles.
- Magnesium is vital for healthy bones and teeth. Around 70 per cent of the body’s magnesium is stored in the bones and teeth, and most of this is found in the crystals that are responsible for bone’s hardness and rigidity.
- Magnesium supports energy metabolism in the body. This means it contributes to our body’s ability to create energy from the food that we eat.
- Magnesium contributes to normal psychological function – how we feel and our mood, and even how we’re affected by stress.
- Magnesium is needed in the process of cell division. This means it’s necessary for all processes of growth and repair in the body.
- Magnesium may be needed for proper absorption of calcium and calcium homeostasis (maintaining a steady level of calcium in the body) [2,3]. This means that it’s important to make sure we’re getting enough magnesium when we take calcium supplements.
Magnesium may also play a role in healthy blood pressure , normal heart rhythm, supporting insulin sensitivity (healthy blood glucose levels) and supporting sleep, among many other potential roles [3,5].
How much magnesium do we need?
The nutrient reference value for magnesium in the UK is 375 mg for adults. Nutrient reference values refer to the amount needed to ensure that the needs of nearly all the population (97.5%) are being met.
The best common food sources of magnesium are:
- Pumpkin seeds. These nutrient-rich seeds may contain over 500mg of magnesium per 100g, which is equivalent to about 70mg per tablespoon – around 20 per cent of our recommended daily intake.
- Other nuts and seeds including (in order of magnesium content, highest first) flax seeds, Brazil nuts, sesame seeds and tahini, sunflower seeds, cashews and almonds. Most seeds and nuts are best eaten ground or in a paste (e.g. tahini or nut butter) to make the minerals such as magnesium more absorbable.
- Beans and pulses including mung beans, pinto beans, kidney beans, peanuts, and lentils. Their magnesium content varies from 120mg to 190mg per 100g, but this is dry weight, so the average serving would provide around half of this amount.
- Grains and grain flours, especially rye, quinoa, buckwheat and oats.
- Green vegetables: kale, spinach and chard. These contain around 80mg of magnesium per 100g, which may be a lot less than seeds or beans, but it’s easier to eat more of them.
Deficiency signs and symptoms*
Some researchers say magnesium deficiency is quite rare . However, others have found that magnesium intakes in industrialized countries are below recommended daily intakes – one reason being the increased consumption of processed foods.[4,5]
Deficiency symptoms may include [3,5]:
- Anxiety and irritability
- Muscle weakness, cramps, tremors or twitching
- Mood changes, such as depression
- Rapid heartbeat
- Poor appetite
*If you experience any of these symptoms, please consult your doctor or health practitioner.
Forms and bioavailability / What to look for when buying a supplement
When looking at magnesium supplements, it’s important to note that some forms of magnesium are more absorbable than others.
- Magnesium oxide can be a common form used in cheaper supplements. It is generally thought to be poorly absorbed – one study found as little as 4 per cent is absorbed! If you see a magnesium supplement providing more than about 200mg per tablet or capsule, it’s likely to be primarily in the form of magnesium oxide and therefore may not be the best choice.
- Magnesium citrate has been found to be significantly more absorbable and bioavailable than magnesium oxide , and so is considered a better choice. It’s relatively inexpensive and so is easy to find in supplements. Unlike magnesium oxide, magnesium citrate products often contain only 100 or 150mg of magnesium per tablet/capsule, so you may need to take more than one per day to reach the advised daily dose on the label. In higher doses or in sensitive individuals, magnesium citrate may loosen the bowels.
- Magnesium glycinate is magnesium attached to glycine, an amino acid, and is also known as ‘chelated magnesium’. Magnesium glycinate is considered a very good form of magnesium for absorption. One of its advantages is that it may be gentler on the digestive system than magnesium citrate, and not as likely to cause loose stools. As glycine has been investigated for its potential to support sleep , magnesium glycinate may be a good choice if you need help in this area.
- Magnesium malate and magnesium gluconate and are other forms sometimes found in supplements, and are also considered well absorbed. Malate in particular may have a similar effect to citrate in terms of its effect on the bowels.
- ‘Food form’ magnesium is found in a small number of supplements. It is a natural form of magnesium that may be better absorbed and utilised in the body than ‘isolated’ magnesium (as found in most supplements).
In summary, our top recommendations are magnesium glycinate (chelated magnesium) and food-form magnesium, followed by citrate, malate and gluconate. Malate and citrate may be chosen if the person has slow digestive transit (constipation), whereas glycinate or food-form may be better for someone who needs a form that’s gentler on the digestive system.
Dosages: Lifestyle Labs’ recommendations
Adults: Magnesium supplements for adults typically provide between 100 and 400 mg per daily dose (which maybe two or three tabs/capsules). The ideal amount to take can be very individual: some people find they do well on just a small amount, and some regularly take 300 or 400mg. For most people, anywhere within this range is considered safe for daily use as long as it is not causing loose stools; however if you’re regularly taking over 300mg, we would advise making sure you’re getting a good source of other minerals either in a nutrient-rich diet, or in a multi-mineral or multivitamin/mineral supplement taken at a different time of day to the magnesium. Taking more than 400mg per day is not advisable unless recommended by a practitioner.
Children: There are small number of magnesium supplements on the market suitable for children under 12 – they tend to provide up to about 100 or 125mg per daily dose. More than this may be recommended by a healthcare practitioner.
If you are taking any medications or have any medical condition, please consult your healthcare practitioner before taking magnesium.
Magnesium is generally a very safe supplement to take for most people. The primary sign that you’ve taken too much is loose stools – if this happens, lower the dose, or choose one of the gentler forms of magnesium, as we saw above.
- Kass L, Weekes J, Carpenter L. Effect of magnesium supplementation on blood pressure: a meta-analysis. Eur J Clin Nutr. 2012 Apr;66(4):411-8. doi: 10.1038/ejcn.2012.4.
- http://lpi.oregonstate.edu/mic/minerals/magnesium. [This link leads to a website provided by the Linus Pauling Institute at Oregon State University. Lifestyle Labs is not affiliated or endorsed by the Linus Pauling Institute or Oregon State University.]
- Osiecki, H. (n.d.). The Nutrient Bible. 9th ed. Bio Concepts Publishing, pp.182–183.
- Sabatier M et al. Meal effect on magnesium bioavailability from mineral water in healthy women. Am J Clin Nutr. 2002 Jan;75(1):65-71.
- Haas, E. and Levin, B. (2006). Staying healthy with nutrition. Berkeley: Celestial Arts. p.165
- Weller E et al. Lack of effect of oral Mg-supplementation on Mg in serum, blood cells, and calf muscle. Med Sci Sports Exerc. 1998 Nov;30(11):1584-91.
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001 Dec;14(4):257-62.
- Lindberg JS et al. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990 Feb;9(1):48-55.
- Kawai N et al. The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology. 2015 May;40(6):1405-16.