Magnesium storage, risk of deficiency, supplementation, preferred form... In this article, I'd like to tell you a little more about magnesium, the mineral that is so important yet so deficient in so many of us.
A reminder of biochemistry
Minerals are, as their name suggests, mineral substances contained in food and water. They are involved in many of the body’s reactions and contribute to its proper functioning. Their concentration in the body exceeds 1 mg/kg body weight. Among the most common minerals are calcium, magnesium, sodium, potassium and phosphorus.
Trace elements are substances of mineral origin present in very small quantities in the body (oligo means “small” in Greek). As you can imagine, just because they’re present in smaller quantities doesn’t mean they’re any less important! Among the best-known trace elements are iron, iodine, zinc, selenium, fluorine and others. For simplicity’s sake, we often speak of minerals in everyday language, without distinguishing between them and trace elements, because it’s not easy to remember in what quantities a particular mineral is present in the body.
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Focus on magnesium
It’s certainly the best-known and most widely publicized mineral, and rightly so! It is involved in over 300 enzymatic reactions, and its most emblematic roles include :
- its contribution to bone health (with calcium and phosphorus)
- its role in the proper functioning of the immune system, heart and blood pressure
- its action in muscle transmission
- its contribution to stress management
- its positive effect on glycogen synthesis in the liver (glycogen is our most readily available source of energy, especially for physical exercise).
For sportswomen, magnesium is essential because it helps to :
- regulation of neuromuscular excitability
- stress and sleep management
- energy production and transmission.
Where is magnesium stored in the human body?
Your body contains around 25 g, 99% of which is in bone and soft tissue. Only 1% circulates in the extracellular fluid (the liquid in which cells, notably blood plasma, are immersed). As you can see, measuring magnesium in a blood test doesn’t mean much, and is certainly not diagnostic.
How can you tell if you’re magnesium deficient?
There are several signs to suggest magnesium deficiency, the best known being :
- involuntary muscle spasm of the eyelid or lip
- cramp.
However, it’s the accumulation of several symptoms that can tip the balance towards a deficiency, rather than a single sign taken in isolation. If in doubt, consult your doctor.
Why are sportswomen particularly at risk of deficiency?
Sportswomen are particularly at risk of magnesium deficiency, as are many other microelements (vitamins and minerals).
Indeed, particularly in endurance sports, certain needs are increased, including those for magnesium, for the following reasons:
- Poor assimilation : if your intestines are in poor condition, you risk poorly absorbing some of the nutrients you ingest (ingesting and absorbing are two different things).
- Increased needs: some people have a tendency to over-consume nutrients, and intensive sport can exacerbate this phenomenon. This is particularly true of magnesium, but also of B vitamins.
- Lack of intake : if your diet is unbalanced, particularly if you don’t eat fresh fruit and vegetables, whole and semi-complete starches, or legumes. What’s more, cooking with water can accentuate losses of this mineral.
Where can I find it?
A varied, balanced diet, rich in raw and cooked fresh seasonal vegetables and fruit, whole and semi-complete starches and legumes, seeds and oilseeds, will provide you with the magnesium you need.
However, magnesium is generally poorly absorbed , and also competes with calcium. Increased stress, intensive sports activities and the use of oral contraceptives all increase magnesium requirements… bearing in mind that at least 75% of the French population is deficient!
The most interesting sources of magnesium are wholegrain cereals (especially buckwheat, oats, rye and brown rice), as well as legumes (particularly lentils, chickpeas and white beans). Seafood and oilseeds (Brazil nuts, almonds) also contain good quantities.
Cocoa is also an interesting source! Unfortunately, the magnesium in chocolate is poorly absorbed, and if we wanted to cover our daily needs with just 70% cocoa dark chocolate, we’d have to swallow… 2 100 g bars for men, and 1.5 bars for women!
Should I take supplements?
In the event of a magnesium deficiency diagnosed by a physician, but also in the case of obvious clinical signs already mentioned (e.g. eyelid or lip spasms), a well-chosen supplement will prove useful. It can be taken on an occasional or long-term basis. This is all very personal and requires a global approach.
Good to know: Supplementation is used to make up for a deficiency, while supplementation supports the body in certain specific situations, including sport.
Which form of magnesium should I choose?
The recommended daily dose is 6 mg per kg of body weight (or even 8 mg for regular athletes).
The “bisglycinate” (a magnesium salt that is very well assimilated), “malate” or “citrate” forms (buffering the acidity produced during exercise) are the most interesting.
Take doses of 300 mg a day for at least 2 months, if possible spreading them out over the day (morning, noon and evening, for example). This will enable you to assimilate it better.
While magnesium is essential to our bodies, there’s no point in consuming more than physiological doses (between 300 and 380 mg per day for adults with “normal” physical activity), because what’s absorbed in excess will be eliminated naturally by our bodies (in other words, you’re throwing money down the drain – or, more accurately, down the toilet!).
Finally, to further improve the absorption of the magnesium you take, check that the supplement also includes vitamin B6 and taurine, or even methionine, all at physiological doses (max 100% RDA).
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