In 30 seconds
- An adult’s body stores about 25 g of this mineral, 50-60% of it in the bones. EFSA sets an adequate intake of 350 mg a day for men and 300 mg for women.
- For foods that are a source of magnesium, the EU authorises, among others, this claim: “Magnesium contributes to a reduction of tiredness and fatigue.”
- In older people, a meta-analysis found that with magnesium they fell asleep about 17 minutes sooner than with placebo.
- In athletes, four small studies point to less muscle pain and lower markers of muscle damage with 350-500 mg a day.
If you train, magnesium matters at two points in your day: recovery after exercise and rest at night. It has official health claims for the nervous system, muscles and tiredness, and interesting studies in athletes and on sleep. This is what the data say, outcome by outcome. If you are after the practical answer, you will find it in what magnesium is good for.
What it is and where it is found
An adult’s body stores about 25 g of this mineral, 50-60% of it in the bones and almost all the rest in soft tissues, such as muscle. Less than 1% is in the blood, and the body keeps that level tightly controlled 1.
It takes part in more than 300 reactions in the body and is needed by the neuromuscular and cardiovascular systems 2. Among other things, it helps move calcium and potassium across cell membranes, a key step for nerve impulses, muscle contraction and a normal heart rhythm 1.
Forms of magnesium
Which forms were absorbed better
How much you need
EFSA sets an adequate intake of 350 mg a day for men and 300 mg for women 2. Nuts, seeds, cocoa, pulses, wholegrains and vegetables are good sources 3:
| Food | Portion | Magnesium |
|---|---|---|
| Roasted pumpkin seeds | 28 g | 156 mg |
| Chia seeds | 28 g | 111 mg |
| Roasted almonds | 28 g | 80 mg |
| Boiled spinach | Half a cup | 78 mg |
| Roasted cashews | 28 g | 74 mg |
| Cooked black beans | Half a cup | 60 mg |
| Baked potato with skin | 100 g | 43 mg |
| Plain low-fat yoghurt | 227 g | 42 mg |
Source: NIH, Office of Dietary Supplements. Portions converted from ounces to grams (1 ounce = 28 g).
- Absorption: of what you eat, normally 30-40% is absorbed 1.
- Forms: in small studies, citrate, aspartate, lactate and chloride were absorbed better than oxide and sulphate 1.
- From 40 onwards: with age, the gut absorbs less magnesium and the kidneys excrete more 1.
- If you train intensively: the authors of a review in athletes suggest that 10-20% more is needed than in sedentary people 9.
The functions the EU recognises
The European Union authorises, among others, these health claims for foods that are at least a source of magnesium 4:
- “Magnesium contributes to normal functioning of the nervous system”.
- “Magnesium contributes to normal muscle function”.
- “Magnesium contributes to a reduction of tiredness and fatigue”.
A varied and balanced diet and a healthy lifestyle are important.
Level of evidence by outcome
| Outcome | Evidence | What the data show |
|---|---|---|
| Nervous system, muscles and tiredness | High | Authorised health claims in the EU for foods that are a source of magnesium. |
| Time to fall asleep in older people | Low | About 17 minutes less than with placebo in 2 trials; low certainty according to the authors. |
| Sleep quality in adults who sleep poorly | Preliminary | Improvements in two recent placebo-controlled trials, with bisglycinate and with L-threonate. |
| Muscle pain and recovery | Preliminary | Less muscle soreness and lower markers of muscle damage in 4 small studies with athletes. |
| Muscle cramps | Low | In older people with cramps of no known cause, no difference compared with placebo. There are no trials on exercise-related cramps. |
The rating is our own, based on the number of studies, their quality and the consistency of the results.
The key studies
| Study | Type | Sample | Outcome |
|---|---|---|---|
| Mah and Pitre, 2021 | Meta-analysis | 3 trials, 151 older people | 320-729 mg a day, as oxide or citrate, for 20 days to 8 weeks: they fell asleep about 17 minutes sooner than with placebo. 5 |
| Abbasi et al., 2012 | Placebo-controlled trial | 46 older people | 500 mg a day for 8 weeks: better sleep efficiency, less time to fall asleep, more melatonin and less cortisol in the blood. 6 |
| Schuster et al., 2025 | Placebo-controlled trial | 155 adults aged 18 to 65 who slept poorly | Bisglycinate providing 250 mg of magnesium a day for 4 weeks: a 3.9-point improvement on their sleep scale, compared with 2.3 with placebo. 7 |
| Hausenblas et al., 2024 | Placebo-controlled trial | 80 adults aged 35 to 55 | 1 g a day of magnesium L-threonate for 21 days: better deep sleep and REM scores, more energy and better mood. 8 |
| Tarsitano et al., 2024 | Systematic review | 4 studies, 73 athletes | 350-500 mg a day, for 7 days to 8 weeks: less muscle pain and lower markers of muscle damage. 9 |
| Garrison et al., 2020 | Cochrane review | 11 trials, 735 people | In older people with cramps of no known cause, no difference compared with placebo. In pregnancy, conflicting results. 10 |
Magnesium and sleep
What the sleep studies found
Magnesium and sleep
The authors of one of the trials describe magnesium as a natural regulator of two brain systems involved in sleep: it dampens the NMDA receptor, which activates neurons, and supports the action of GABA, which calms them 6.
In older people, a meta-analysis of 3 trials with 151 participants found that with magnesium they fell asleep about 17 minutes sooner than with placebo. Total sleep time rose by 16 minutes, a difference that did not reach significance 5. In the Abbasi trial, blood melatonin also rose and cortisol fell 6.
The two most recent trials are in adults who slept poorly. With bisglycinate, which binds magnesium to glycine, 155 adults improved their sleep score by 3.9 points in 4 weeks, compared with 2.3 with placebo, taking it between 30 and 60 minutes before bed 7. With L-threonate, 80 adults aged 35 to 55 improved their deep sleep and REM scores, measured with a sleep-tracking ring 8.
We put it in practical terms in magnesium for sleep.
Magnesium, muscle and recovery
A systematic review brought together the studies that used magnesium alone in active people: 4 studies with 73 athletes aged 19 to 27, with 350-500 mg a day for 7 days to 8 weeks 9.
- Muscle soreness: in the bench press study, muscle pain fell compared with baseline at 24, 36 and 48 hours with 350 mg a day, and perceived recovery improved. In runners, there was also less pain after a demanding downhill run 9.
- Muscle damage: in basketball players and in cyclists during a stage race, markers of muscle damage were lower 9.
These are small studies, and the authors call for larger trials to pin down the form, timing and dose 9.
What about cramps?
It is one of the most common questions. The Cochrane review brought together 11 trials with 735 people. In older people with cramps of no known cause, magnesium showed no difference compared with placebo. In pregnancy, the results are conflicting, and there are no trials on exercise-related cramps 10.
We explain what causes them and what to do in muscle cramps during exercise.
Magnesium a day
What you need and the limit for supplements
Safety
- Limit for supplements: the one used in Europe is 250 mg a day of magnesium from supplements, not counting what comes from food. It is set to avoid mild diarrhoea 3.
- Adverse effects: in the cramp trials, the most common were digestive, such as diarrhoea 10.
- Medication: magnesium can interfere with some antibiotics and with medicines for the bones, and diuretics and stomach-protecting medicines taken for a long time can lower its level 1. If you take medication or have kidney disease, check with your doctor.
Frequently asked questions
What is magnesium good for?
It takes part in more than 300 reactions in the body. “Magnesium contributes to normal functioning of the nervous system.” “Magnesium contributes to normal muscle function.” “Magnesium contributes to a reduction of tiredness and fatigue.”
How much magnesium should you take a day?
EFSA sets an adequate intake of 350 mg a day for men and 300 mg for women, counting everything you eat. For magnesium from supplements, the upper limit used in Europe is 250 mg a day.
Which type of magnesium is absorbed best?
The forms that dissolve well. In small studies, citrate, aspartate, lactate and chloride were absorbed better than oxide and sulphate.
Does magnesium help you sleep?
The studies are promising: in older people, with magnesium they fell asleep about 17 minutes sooner than with placebo, and two recent trials in adults who slept poorly found improvements compared with placebo.
Does magnesium stop cramps?
In older people with cramps of no known cause, the Cochrane review found no difference compared with placebo. There are no trials on exercise-related cramps.
Sources
- Office of Dietary Supplements, National Institutes of Health. Magnesium: fact sheet for health professionals. View publication
- EFSA. Dietary reference values: magnesium and phosphorus. Press release from the European Food Safety Authority, 28 July 2015. View publication
- Nordic Council of Ministers. Nordic Nutrition Recommendations 2023: magnesium. Nord 2023:003. View publication
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. View publication
- Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complement Med Ther. 2021;21:125. View publication
- Abbasi B, Kimiagar M, Sadeghniiat K, Shirazi MM, Hedayati M, Rashidkhani B. The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. J Res Med Sci. 2012;17(12):1161-1169. View publication
- Schuster J, Cycelskij I, Lopresti A, Hahn A. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep. 2025;17:2027-2040. View publication
- Hausenblas HA, Lynch T, Hooper S, Shrestha A, Rosendale D, Gu J. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial. Sleep Med X. 2024;8:100121. View publication
- Tarsitano MG, Quinzi F, Folino K, et al. Effects of magnesium supplementation on muscle soreness in different type of physical activities: a systematic review. J Transl Med. 2024;22:629. View publication
- Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;(9):CD009402. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
