Magnesium supplements promise energy, better sleep, improved focus and more – but do they really work?

What is magnesium?

Magnesium is a mineral that plays an active role in countless processes in the body, including how we turn the food we eat into energy. It also works with calcium and vitamin D to support the health of bones and teeth, as well as improving muscle and cognitive function.

How much magnesium does the body need?

Magnesium is a micronutrient, meaning that the body only needs very small amounts at a time. The HSE suggests that for adults aged 19 to 64, the recommended daily allowance is 300mg a day for men and 270mg a day for women.

There is magnesium in whole grains, vegetables, legumes, nuts and dark chocolate. Anyone with a varied and balanced diet, should be able to get all the magnesium needed without taking a supplement.

What are the signs of magnesium deficiency?

The symptoms of magnesium deficiency are rather vague, including headaches, cardiac arrhythmia (irregular heartbeat), increased anxiety, weakness and muscle twitching or cramps. Because of this, it is important to discuss any health concerns with your GP rather than simply taking a supplement, as these issues may be caused by other conditions.

“It is often thought that magnesium helps with muscle cramps. For that reason, I was prescribed it by my GP as a child,” says Professor Wim Derave, exercise physiologist and sports nutritionist at Ghent University. “However, it has now been shown that a magnesium deficiency is not the primary cause of that problem and a magnesium pill therefore does not offer a solution.”

Dr Dirk Devroey, professor of general medicine at VUB hospital in Brussels, sees a magnesium deficiency in a number of profiles: alcoholics; older people who do not eat enough; patients with uncontrolled diabetes; a poorly functioning parathyroid gland or Crohn’s disease.

According to Dr Devroey, some medicines can also contribute to a magnesium deficiency. “I’m thinking of proton pump inhibitors, which are intended to slow down the production of stomach acid. There is also a risk of a deficiency with diuretic medicines, the medicines that people receive after an organ transplant and with some chemotherapy treatments. This usually manifests itself in symptoms such as fatigue and lethargy.”

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Do magnesium supplements help fatigue?

Though including a healthy amount of magnesium in your diet can help support energy levels, supplements are not necessarily a quick fix for anyone feeling lethargic. ​

“Most people who suffer from fatigue do not have a magnesium deficiency,” Dr Devroey states. In the same, way, magnesium is thought to support cognitive function, but short-term use of supplements is unlikely to offer a noticeable improvement in focus and memory.

“Magnesium supplements are often recommended to students during the study period,” Dr Devroey says. “I have to disappoint them: the tablets are really not going to improve their study results.”

What do scientific studies say about magnesium supplementation?

As a sports nutritionist, Prof Derave has seen studies in which athletes took magnesium pills. “The researchers found no evidence that they would work. What we did see then is that you can lose magnesium through extreme sweating.

“If riders in the Tour de France race in the heat, a magnesium deficiency can occur. (But) it is important to point out that such a rider eats three times as much in a Grand Tour as a normal person. So the risk is not that great. As sports nutritionists, we therefore pay little attention to magnesium, but we are much more alert to iron and vitamin D.”

Together with Ghent University colleagues from the Faculty of Pharmacy, Prof Derave also compared various magnesium supplements.

“That study revealed that magnesium in some products is poorly absorbed by the body. There are two types of magnesium: inorganic and organic. Many manufacturers use the first type. It is extremely weak and is immediately excreted in your stool, so the mineral never enters your blood. It hardly dissolves in your intestines. With such a pill, you only produce expensive bowel movements.”

Can you take too much magnesium?

As with all supplements, there are possible side effects of taking too much magnesium, defined as more than 400mg per day.

According to the HSE, there is “not enough evidence” to know the possible effects of taking high doses of magnesium long-term, but more immediate issues can include diarrhoea.

“If you take too much, it can cause diarrhoea, abdominal pain, low blood pressure, muscle weakness and drowsiness,” warns Dr Devroey.

“I certainly wouldn’t take them if your kidneys are not working properly, because you don’t pee out enough magnesium. Besides, as with most nutritional supplements, you pay for something you don’t need. That seems like enough damage to me.”

Should I consider taking a magnesium supplement?

Magnesium supplements are often marketed as the miracle cure for a long list of ailments including low energy, muscle tension and trouble sleeping. But there is not enough scientific evidence to suggest that taking magnesium pills will make a significant difference to wellness for most people.

Though it is important to maintain a varied and balanced diet that will help you to get the recommended amounts of magnesium — as well as other vital vitamins and minerals — the average healthy person does not have a magnesium deficiency.

However, if you are concerned about your magnesium levels, or possible symptoms such as low energy levels, it’s best to see your GP. You should also seek medical advice if you want to start taking any supplements, as they may interact with other medications you are using.