Find out all about magnesium, including what it does, how much you need, where to find it and who might need to supplement their diet
Written by Jack Feeney on December 11, 2018
Reviewed by Fiona Hunter on January 3, 2019
Overview of magnesium
What is magnesium and what does it do?
Magnesium is one of the most abundant minerals in your body. It’s needed for hundreds of processes,1 including:
- supporting the nervous system
- breaking down food into nutrients
- muscle function, including heart muscle
- maintaining electrolyte balance
- healthy bones and teeth
- normal cell division2
A magnesium deficiency is rare, but symptoms include loss of appetite, nausea and fatigue.3
Magnesium-rich foods include green leafy veg and wholemeal bread, so most people get all they need from their diet.4 It’s also available as tablets, capsules or a spray, or as part of a multi-vitamin.
Functions of magnesium
What does magnesium do in the body?
Magnesium benefits many enzymes in the body, some of which are responsible for converting the food you eat into energy. The mineral is especially important for breaking protein down into amino acids.5
Because it’s so important for energy release, this makes magnesium critical to many other processes in the body – for example, the nervous system and release of neurotransmitters, or chemical messengers.
Magnesium is also needed for muscle contraction and relaxation, including the muscles in your heart.6 Magnesium works as a natural blocker to calcium – which triggers muscle contractions – helping the cells relax.7
Magnesium also plays a key role in the structural development of our bones. A 2014 study by the American Journal of Clinical Nutrition Scientists reported that a magnesium deficiency is associated with low bone density.8 This can put you at risk of bone-thinning conditions such as osteoporosis.
How much magnesium do I need?
Women need 270mg a day, while breast-feeding women need an extra 50mg a day. Men need 300mg a day.9,10 That’s about the amount found in 30g of pumpkin seeds, an avocado, a banana or an 80g portion of spinach.
How much magnesium do children need?
- 1-3 years – 85mg a day
- 4-6 years – 120mg a day
- 7-10 years – 200mg a day
- 11-14 years – 280mg a day
- 15-18 years – 300mg a day11
Which foods are the best sources of magnesium?
Plants are the best food sources of magnesium, such as:12
- pumpkin seeds
- nuts – like almonds, cashews and peanuts
- soya products, like soya milk and cheese
- legumes, for example edamame and black beans
- wholegrains, including wholemeal bread, brown rice and quinoa
What are the symptoms of a magnesium deficiency?
Magnesium deficiency is rare as it is found in so many of the foods we eat every day. Our kidneys also help to regulate magnesium levels in the body by limiting the amount we lose when we urinate.13
Early signs and symptoms of magnesium deficiency include:14
- appetite loss
Symptoms of a moderate deficiency include numbness, tingling and an abnormal heart rhythym.15
Who is most at risk of magnesium deficiency?
About 40% of girls aged 11 to 18 years have low magnesium levels, according to the 2011 National Diet and Nutrition Survey.16 People who abuse alcohol, older adults and people with type 2 diabetes could be more susceptible to magnesium deficiency as they may not absorb enough of the nutrient.17
What happens if I consume too much magnesium?
Taking high doses of magnesium of more than 400mg a day for short periods can lead to diarrhoea, according to the NHS.18 This means you should be careful about how much magnesium you consume from supplements.
When should I take a magnesium supplement?
If you eat a balanced diet with a wide range of foods every day, you should get all the magnesium you need.
Should children take magnesium supplements?
Children should be able to get all the magnesium they need from their diets.
Should women take a magnesium supplement during pregnancy?
You can get all the magnesium you need from your diet during pregnancy. However, a 2017 report in Advanced Biomedical Research found that many pregnant women are deficient in this mineral. Ask your GP for a blood test if you think you may have low levels of magnesium.19
What are the potential benefits of taking magnesium supplements?
As magnesium is important for a healthy nervous system, low levels may be linked to the development of migraine. A 2012 study in Journal of Neural Transmission found that up to half of people with migraine were deficient in the mineral.20
With 60% of magnesium stored in our bones, research also shows that a diet containing enough magnesium can help lower the risk of developing osteoporosis. It’s thought magnesium deficiency impacts bone cells and crystal formation, and increases inflammation.21
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.
1. Medline Plus. Magnesium in diet
2. European Commission. EU Register on nutrition and health claims
3. HSIS. Magnesium
4. NHS. Magnesium
5. Jahnen-Dechent W, Ketteler M. Magnesium basics
6. As above
7. Ryan Raman. Healthline. What Does Magnesium Do For Your Body?
8. Orchard TS, et al. Magnesium intake, bone mineral density and fractures: results from the Women’s Health Initiative Observational Study
9. NHS. Others: vitamins and minerals
10. Helena Gibson-Moore. Nursing in Practice. Diet and nutrition requirements when breastfeeding
11. Public Health England. Government Dietary Recommendations
12. National Institutes of Health. Magnesium
13. As above
14. As Source 3
15. As Source 1
16. Whitton C, et al. National Diet and Nutrition Survey: UK food consumption and nutrient intakes from the first year of the rolling programme and comparisons with previous surveys
17. As Source 1
18. As Source 3
19. Zarean E, Tarjan A. Effect of Magnesium Supplement on Pregnancy Outcomes: A Randomized Control Trial
20. Mauskop A, Varughese J. Why all migraine patients should be treated with magnesium
21. Castiglioni S, et al. Magnesium and Osteoporosis: Current State of Knowledge and Future Research Directions