Magnesium
Magnesium is a mineral involved in hundreds of processes in your body, from turning food into energy to making your muscles and nerves work and keeping your bones healthy.
On this page
Why magnesium matters
- Energy. It helps turn the food you eat into energy.
- Muscles and nerves need it to contract and relax properly.
- Bones. About half your magnesium is stored in your skeleton1.
How much you need
You should be able to get all you need from a varied diet. If you take a supplement, taking 400 mg a day or less is unlikely to cause harm; more can cause diarrhoea2.
Who might run low: people with gut conditions such as Crohn's or coeliac disease, type 2 diabetes, alcohol dependence, older adults, and people on some long-term medicines like acid-reducing PPIs or certain diuretics1.
Richest food sources
| Food | Per 100 g | Per serving | % daily |
|---|---|---|---|
| Pumpkin seeds | 592 mg | 178 mg30 g | 59% |
| Chia seeds | 335 mg | 50.2 mg1 tbsp (15 g) | 17% |
| Cashews | 292 mg | 87.6 mg30 g | 29% |
| Almonds | 270 mg | 81 mg30 g | 27% |
| Dark chocolate, 70–85% | 228 mg | 45.6 mg20 g | 15% |
| Spinach, boiled | 87 mg | 69.6 mg80 g | 23% |
| Wholemeal bread | 76 mg | 60.8 mg2 slices (80 g) | 20% |
| Black beans, boiled | 70 mg | 105 mg150 g | 35% |
| Edamame beans | 64 mg | 51.2 mg80 g | 17% |
| Brown rice, boiled | 43 mg | 77.4 mg180 g | 26% |
| Banana | 27 mg | 32.4 mg1 medium (120 g) | 11% |
Nuts, seeds, wholegrains, beans and leafy greens are the best bets. See Nuts and seeds and Whole grains.
Signs of low magnesium, and myths
Real deficiency is rare in healthy people. Early signs include loss of appetite, nausea, tiredness and weakness; more severe deficiency can cause tingling, muscle cramps and an irregular heartbeat, and needs a doctor1.
MythMagnesium supplements stop muscle cramps.
FactFor typical muscle cramps in older adults, a Cochrane review found magnesium unlikely to help meaningfully6.
MythEpsom salt baths top up your magnesium.
FactThere's little evidence that meaningful amounts of magnesium are absorbed through the skin7. Enjoy the bath, but eat your magnesium.
Track this in NutriLog
Snack smarter
Scan nuts, seeds and wholegrain snacks to see their calories and traffic lights, and save the ones you like.
Free to use. No card needed.
References
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. ods.od.nih.gov.
- NHS. Vitamins and minerals: Others (including magnesium). nhs.uk.
- Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom (Report on Health and Social Subjects 41). HMSO, London, 1991.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. fdc.nal.usda.gov.
- Public Health England. McCance and Widdowson's The Composition of Foods Integrated Dataset (CoFID). GOV.UK, 2021.
- Garrison SR, Korownyk CS, Kolber MR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;9:CD009402. doi:10.1002/14651858.CD009402.pub3
- Gröber U, Werner T, Vormann J, Kisters K. Myth or reality: transdermal magnesium?. Nutrients. 2017;9(8):813. doi:10.3390/nu9080813