In short:
- Magnesium contributes in particular to a reduction of tiredness and fatigue, to normal muscle function and to the normal functioning of the nervous system, according to the EU register of claims.
- The label reference value is 375 mg a day, including food; EFSA sets 250 mg a day as the amount of magnesium from supplements not to exceed.
- Nuts, seeds, pulses, whole grains and dark chocolate are good sources.
- As a supplement, look at the form (bisglycinate, citrate, oxide) and the amount of elemental magnesium per dose.
Magnesium is probably the most recommended supplement in gyms and endurance clubs alike. Cramps, tiredness, stress, recovery: it is credited with a lot. Some of these roles are genuinely recognised, others are marketing talk. This fact sheet sets out what is established.
Magnesium at a glance
| Benchmark | Value |
|---|---|
| Family | Mineral (macromineral) |
| Authorised roles | Reduction of tiredness, normal muscle function, normal functioning of the nervous system, maintenance of normal bones |
| Reference value (labels) | 375 mg a day (NRV) |
| Adequate intake for adults (EFSA) | 350 mg a day for men, 300 mg for women |
| Limit for supplements | 250 mg a day of magnesium from supplements (EFSA) |
| Food sources | Nuts, seeds, pulses, whole grains, dark chocolate, some mineral waters |
The role of magnesium in the body
Magnesium is a mineral found throughout the body, largely in bones and muscles. It is involved in hundreds of reactions, notably in energy production and muscle contraction.
The EU register of claims1 recognises a large number of claims for magnesium. Magnesium contributes:
- to a reduction of tiredness and fatigue;
- to electrolyte balance;
- to normal energy-yielding metabolism;
- to the normal functioning of the nervous system;
- to normal muscle function;
- to normal protein synthesis;
- to normal psychological function;
- to the maintenance of normal bones and teeth;
- and it has a role in the process of cell division.
You will notice that the word “cramp” does not appear: no claim covers cramps as such.
How much magnesium do you need per day?
| Reference | Value per day |
|---|---|
| Nutrient reference value, used on labels | 375 mg |
| Adequate intake for adult men according to EFSA | 350 mg |
| Adequate intake for adult women according to EFSA | 300 mg |
| Safety limit for magnesium from supplements | 250 mg |
Reference values are published by EFSA2 and, for France, by ANSES3. They concern total intake, including food.
The best food sources of magnesium
Before the supplement comes your plate. The foods richest in magnesium are:
| Food | Why it is useful |
|---|---|
| Almonds, Brazil nuts, cashews | Very rich in magnesium, easy to eat as a snack |
| Pumpkin, flax and chia seeds | Concentrated in magnesium |
| Pulses (lentils, chickpeas, beans) | Magnesium, fibre and plant protein |
| Whole grains | Much richer than their refined versions |
| Dark chocolate | High magnesium content, to enjoy in moderation |
| Some mineral waters | Content stated on the label, in mg per litre |
For the exact content of each food, use the ANSES Ciqual table4. The article on micronutrition and diet explains how to build a mineral-rich plate.
Forms of magnesium in supplements
This is where labels get confusing. The magnesium in a supplement is always bound to another molecule, and the amount of elemental magnesium varies with the form.
| Form | What to know |
|---|---|
| Magnesium oxide | Rich in elemental magnesium, often considered harder on digestion |
| “Marine” magnesium | Usually oxide or hydroxide from seawater: check the exact form |
| Magnesium citrate | Very common organic form |
| Magnesium bisglycinate | So-called chelated form, often chosen for its digestive tolerance |
| Malate, lactate, pidolate | Organic forms, less common |
| Magnesium chloride | Often sold as a powder or in sachets |
Do not stop at the brand name: look at the form and the amount of elemental magnesium per dose, expressed as a percentage of the reference value. The guide on how to choose a food supplement brand details how to read the label.
Common combinations
Many supplements combine magnesium with vitamin B6, which also contributes to a reduction of tiredness and to the normal functioning of the nervous system, or with taurine. This is the case, for example, of Nutripure’s magnesium taurine B6, a brand featured in the ranking of the best food supplement brands. Watch out for overlapping vitamin B6 if you already take a multivitamin.
Magnesium and sport
Magnesium contributes to normal muscle function and to electrolyte balance, two topics that matter to athletes. A supplement, however, only makes sense if your dietary intake is insufficient. With sustained training and a diet rich in nuts, pulses and whole grains, needs are often covered. The sports nutrition guide reviews the supplements that help with exercise, and the page on vitamin and mineral needs places magnesium among the other micronutrients.
Precautions for use
- Stick to the dose: above 250 mg a day of magnesium from supplements, EFSA notes a risk of digestive effects, such as diarrhoea.
- Kidney failure: magnesium is eliminated by the kidneys. If you have kidney disease, no supplement without medical advice.
- Interactions: magnesium can interfere with the absorption of some medicines. Talk to your pharmacist if you are on treatment.
Frequently asked questions
What does magnesium do?
Magnesium has many authorised claims in Europe. In particular, it contributes to a reduction of tiredness and fatigue, to normal muscle function, to the normal functioning of the nervous system, to normal energy-yielding metabolism, to normal psychological function and to the maintenance of normal bones and teeth.
Which form of magnesium should you choose?
The most common forms are oxide, citrate, bisglycinate, malate, lactate, chloride and so-called marine magnesium. What matters is knowing the form and the amount of elemental magnesium per dose. Organic forms such as citrate or bisglycinate are often preferred for their digestive tolerance, but no claim distinguishes one form from another.
How much magnesium should you take per day?
The nutrient reference value is 375 mg a day, including food. EFSA sets 250 mg a day as the amount of magnesium from supplements not to exceed for adults, above which digestive effects may occur. Beyond these benchmarks, ask a health professional.
When should you take magnesium?
There is no official rule on when to take it. Many people take it with a meal for better digestive tolerance, in one or two doses. Above all, stick to the dose stated on the label.