What do I need to know about magnesium?

By Lucy Jones

What is magnesium?

Magnesium is the fourth most abundant mineral found within the human body (1) and has many roles. This includes being a cofactor for (i.e. helps make up) over 300 enzymes (1,2). Enzymes are essential for supporting chemical reactions within the body. Processes such as energy and DNA production also use magnesium (1,2). The nerves and muscles require magnesium to function properly too.

The parathyroid glands, located in the neck, need magnesium to function properly. This gland produces parathyroid hormones, which regulate calcium and phosphorus levels in the body (4). 

How much magnesium do I need?

According to the NHS and Public Health England guidelines, adult women require 270mg/day and adult men require 300mg/day (3, 5).

Which foods can magnesium be found in?

By eating a varied and balanced diet you are likely to get enough magnesium from food alone. 

Magnesium can be found in the following foods:

• Green leafy vegetables

• Legumes

• Nuts

• Seeds

• Quinoa

• Whole grains, such as wholemeal bread and brown rice

Magnesium deficiency

An analysis of the UK National Diet and Nutrition Surveys (Year 1-6) (NDNS) revealed that magnesium intakes were below the recommendation (6). On average, women consumed only 80.2% of the recommended intake and men 90.8% (6). 

There are many reasons someone may not be reaching their magnesium requirements. It’s been suggested that magnesium levels in soil have declined over the years, potentially having a knock on effect on the amount of magnesium found in food (7).

Other reasons may include health conditions which may reduce magnesium absorption. For example, certain gastrointestinal disorders, such as Crohn’s disease and coeliac disease (2). Some medications may also interfere with magnesium absorption. Individuals with alcohol dependence may also experience magnesium deficiency (2). 

Signs and symptoms of magnesium deficiency include (2):

• Loss of appetite

• Nausea

• Vomiting

• Fatigue

• Weakness

In more extreme cases, numbness, tingling and an abnormal heart beat may be experienced (2).

Eating a varied, balanced diet is essential to prevent magnesium deficiency. Given that, according to the NDNS, magnesium intakes were 10-20% below recommendations, it’s likely that focusing on including more food sources of magnesium will be sufficient to boost magnesium intakes, in many instances. Where appropriate, take a food first approach before looking at supplements.

Magnesium supplements

Always speak to a health professional, such as your GP or a Registered Nutritionist or Dietitian before starting any new supplements. This is important to ensure it’s safe for you to do so.

The NHS advise supplementing with no more than 400mg/day of magnesium (3).

Side effects of magnesium supplementation

Supplementing with more than 400mg/day of magnesium for short periods of time may lead to diarrhoea, nausea and stomach pain (2,3).

The long term effects of excessive magnesium supplementation is unclear, but it could have adverse effects on heart health (2,3). 

Forms of magnesium supplements

There are many forms of magnesium available as supplements. Magnesium citrate, magnesium sulphate, magnesium glycinate and magnesium chloride are suggested to be easily absorbed in the body (2, 8, 9, 12, 14). Whereas, magnesium oxide is less well absorbed in the body (14).

Magnesium citrate and magnesium oxide have reported uses in aiding constipation by offering a laxative effect (10, 11).

Magnesium sulphate is suggested to have fewer side effects (12).

Always speak to a health professional who will be able to determine if magnesium supplementation is necessary. They will be able to inform you of the best form of magnesium to use. Never start taking supplements without discussing this with your health professional first, to avoid any health concerns or contraindications.

Summary

Magnesium is a mineral that plays many crucial roles in the body. Whilst UK intakes of magnesium are slightly below the recommendations, magnesium can be found in many whole foods. This makes prioritising a healthy, balanced diet plentiful in green leafy veg, legumes, nuts and wholegrains important. However, if you’re struggling to meet your magnesium needs through food alone, you may wish to speak with a healthcare professional about magnesium supplements.

References

1. Razzaque MS. Magnesium: Are We Consuming Enough? Nutrients. 2018 Dec 2;10(12):1863. doi: 10.3390/nu10121863. PMID: 30513803; PMCID: PMC6316205. 

2. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/ 

3. https://www.nhs.uk/conditions/vitamins-and-minerals/others/

4. Khan M, Jose A, Sharma S. Physiology, Parathyroid Hormone. [Updated 2022 Oct 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499940/ 

5. https://assets.publishing.service.gov.uk/media/5a749fece5274a44083b82d8/government_dietary_recommendations.pdf

6. Derbyshire E. Micronutrient Intakes of British Adults Across Mid-Life: A Secondary Analysis of the UK National Diet and Nutrition Survey. Front Nutr. 2018 Jul 19;5:55. doi: 10.3389/fnut.2018.00055. PMID: 30073167; PMCID: PMC6060686.

7. Cazzola R, Della Porta M, Manoni M, Iotti S, Pinotti L, Maier JA. Going to the roots of reduced magnesium dietary intake: A tradeoff between climate changes and sources. Heliyon. 2020 Nov 3;6(11):e05390. doi: 10.1016/j.heliyon.2020.e05390. PMID: 33204877; PMCID: PMC7649274.

8. Blancquaert L, Vervaet C, Derave W. Predicting and Testing Bioavailability of Magnesium Supplements. Nutrients. 2019 Jul 20;11(7):1663. doi: 10.3390/nu11071663. PMID: 31330811; PMCID: PMC6683096.

9. Schwalfenberg GK, Genuis SJ. The Importance of Magnesium in Clinical Healthcare. Scientifica (Cairo). 2017;2017:4179326.