Guide to magnesium

Magnesium is one of the most important health-promoting minerals. It's involved in energy production, nerve function, muscle relaxation and bone and tooth formation.

It also helps control the levels of blood glucose and has a useful laxative effect at higher doses.

Healthy adult bodies contain about 25g of magnesium, which puts it in fourth place in mineral rankings. About 99 per cent of magnesium is stored in bones, muscles and non-muscle soft tissue.

When it comes to our bone health, we tend to think of calcium as being important. However, magnesium also makes a significant contribution to the strength of our skeletons, by improving bone density and potentially protecting us from the fragile bone disease osteoporosis.

Dr Sarah Brewer says: ‘Magnesium is a hard-working mineral that is vital for over 300 body enzymes to work properly. We need it for every metabolic process from producing energy to muscle contractions. If we do not obtain enough magnesium in our diet, it can make us feel weak, affect our co-ordination, and cause loss of appetite, and a tendency towards constipation. In these circumstances a magnesium supplement may help.’

What does magnesium do?

Magnesium plays a part in how our body produces energy; in how our cells send messages; and the production of proteins and DNA (the genetic material in every cell). It is also involved in the transport of potassium and calcium across cell membranes. As a result, muscle contraction and having a normal heart rhythm depend on magnesium.

Blood pressure

Several studies have found that taking a magnesium supplement can lower high blood pressure.

This is important, because high blood pressure can put you at greater risk of having a stroke, or coronary heart disease. Having your blood pressure checked, usually at your GP surgery, is the only way to find out if your blood pressure is too high.


In 2016, the number of people in the UK with diabetes rose to over four million. Left untreated or uncontrolled, diabetes can lead to complications such as nerve damage, kidney problems and diabetic retinopathy – and it can also raise your risk of developing heart disease by two to five-fold. For these reasons it is important to take steps to prevent yourself developing this disease.

One large review of 13 studies has shown that a good intake of magnesium, from either food or supplements, significantly reduces the risk of developing type 2 diabetes.

Muscle health

Magnesium is needed for healthy muscle and nerve function. This is important for all of us, but especially for athletes, who expend huge amounts of energy when competing and push their muscles and nerves to the limit. Strenuous exercise increases magnesium requirements by 10 to 20 per cent and its believed athletes may be at risk of deficiency if their magnesium intake is below 260mg for men and 220mg in women. Experts say performance will improve in athletes who are magnesium-deficient if they take a supplement.

Getting magnesium from your diet

Good sources of magnesium include: spinach and other dark green, leafy vegetables; nuts; meat; fish; shellfish; dairy foods such as cheese; bread (wholegrain is best); and brown rice.


The Department of Health's advice is that taking up to 400mg a day of magnesium supplements is unlikely to cause any adverse effects.

Taking too much magnesium can cause diarrhoea.

Correct Dosage

The EU RDA/NRV is 375mg. A typical supplement dose is one 375mg tablet a day.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

Magnesium is a hard-working mineral that is vital for over 300 body enzymes to work properly.

Dr Sarah Brewer


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