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Magnesium nutrient guide: Benefits, foods, deficiency and supplements

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The benefits of magnesium, how you can obtain it through diet, the role of supplements and what can happen if you're deficient.

What is magnesium good for?

Magnesium is a mineral whose importance is growing daily. Researchers once estimated that magnesium was needed for over 300 enzymes to work properly – that number has now grown to over 700. That makes magnesium involved in just about every metabolic reaction, from the production of energy to the synthesis of hormones, proteins and genetic material. It is the fourth most abundant metal in the body overall and is concentrated within cells, where it is the second most abundant mineral after potassium.1

Magnesium is vital because it helps to man the 'pumps' that control how salts move in and out of cells. It is essential for muscle contraction, nerve conduction and the production of energy. In the circulation, it promotes blood vessel dilation, so lowering blood pressure, reducing abnormal blood clotting and protecting against abnormal heart rhythms.

All these beneficial effects may explain why research involving almost 533,000 people found that the risk of cardiovascular events (heart attack, stroke) was 15% lower in those with the highest dietary magnesium intake and 33% lower in those with the highest blood levels of magnesium.2

What foods contain magnesium?

Magnesium is obtained from foods that have not been highly processed. It is found in the outer parts of grains, for example, so if these are removed to produce 'white' flour and rice, much of the magnesium present is stripped out.

As well as wholegrains, magnesium is obtained from eating beans (especially soy), nuts, seafood and dark green, leafy vegetables. Chocolate and drinking water in hard-water areas are also important sources for some people. Even so, lack of magnesium is common.

Magnesium deficiency

The National Diet and Nutrition Surveys show that around 13% of adults have magnesium intakes below the lower reference nutrient intake (LRNI), putting them at risk of deficiency symptoms. The average (median) daily magnesium intake for women was 229mg, for example, yet the EU nutrient reference intake, which meets the needs of most people, is 375mg per day. This is largely due to a diet consisting mainly of processed foods.

Low magnesium symptoms

Lack of magnesium contributes to many common problems such as insomnia, fatigue and weakness, as well as muscle trembling, cramps and constipation.

For people with fibromyalgia, low magnesium levels have been associated with the severity of symptoms. Adding magnesium supplements to medical treatment of fibromyalgia significantly reduced the number of tender points and depression scores compared with medical treatment alone.3

Low magnesium intakes are also associated with a raised blood pressure and poor glucose tolerance.

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Magnesium benefits

Magnesium is one of our most important minerals and offers many benefits throughout the body.


  • Magnesium contributes to normal energy-yielding metabolism
  • Magnesium contributes to a reduction of tiredness and fatigue

Magnesium is a necessary cofactor in hundreds of enzymatic reactions, many of which involve the production of energy from fatty acids and glucose. If you are feeling tired and fatigued, a magnesium supplement may help.

N.B. See your doctor if you have persistent tiredness, which doesn't improve. Occasionally, lack of energy is a sign of health problems that need further investigation and treatment.

Salt balance

  • Magnesium contributes to electrolyte balance

Electrolytes are electrically charged particles (ions) such as sodium, potassium, calcium and bicarbonate. The flow of electrolytes in and out of cells is vital to maintain normal cell function, electrical potentials across cell membranes, muscle contraction and nerve conduction. Magnesium helps to control the flow of sodium and potassium in and out of cells, and is involved in calcium and oxygen transport.

Heart health

This active transport of electrolytes across cell membranes is also a key component of what scientists call nerve impulse conduction, meaning the passage of electrical signals down nerves. These nerve signals are what stimulate our muscles, include the heart muscle to contract, and in the case of the heart to pump blood around our bodies.

As long ago as 2009 these properties led EFSA, the European Food Safety Authority, approving two health claims – that 'Magnesium contributes to normal functioning of the nervous system' and 'Magnesium contributes to normal muscle function.'

More recently (2018) a major review of studies concluded that a higher magnesium intake, either from food or supplements, is linked with protection against major cardiovascular risk factors, including metabolic syndrome, type 2 diabetes, and high blood pressure as well as against stroke and total cardiovascular disease.

Body maintenance

  • Magnesium has a role in the process of cell division
  • Magnesium contributes to normal protein synthesis
  • Magnesium contributes to normal muscle function
  • Magnesium contributes to the maintenance of normal bones
  • Magnesium contributes to the maintenance of normal teeth

Our cells each divide at different rates in order to replace themselves and maintain healthy tissues such as muscles and even our bones. This process, including the synthesis of new proteins, depends on the presence of adequate amounts of magnesium.

Mental health

  • Magnesium contributes to normal functioning of the nervous system
  • Magnesium contributes to normal psychological function

Because magnesium is involved in the movement of electrolytes in and out of cells, it is vital for nerve conduction and our ability to think straight. It helps to calm the nervous system by blocking receptors in the brain (N-methyl D-aspartate or NMDA) to damp down over-excitability.4 Magnesium also has psychological benefits by lifting a low mood.5

Does magnesium help you sleep?

Magnesium has a relaxing effect on muscles and a calming effect on the nervous system. A great way to boost your magnesium levels is to absorb it through your skin. Bathing in magnesium-rich spa waters is a traditional therapy for many health conditions. Just add a handful of magnesium flakes to your bath water, lie back and relax for 20 to 30 minutes before bed to help promote a good night's sleep.

Magnesium supplements

The EU recommended daily amount is 375mg magnesium per day. The upper safe limit for long-term use from supplements is suggested as 400mg per day. The most popular way to take these supplements is as magnesium tablets.


The most common magnesium side effects are a laxative action that can develop above doses of 400mg per day. This is not always a bad thing, of course, and magnesium salts are used medically to help clear the bowel before procedures such as colonoscopy or bowel surgery. If you are sensitive to this effect, reduce the dose (e.g. just take one magnesium tablet if the usual dose is two). You can also add magnesium flakes to your bath for absorption across the skin.

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