Can magnesium supplements improve sleep, energy and concentration?

In the 17th century, wealthy people in England flocked to a well on Epsom Common that was said to contain healing water. It had a bitter taste but a strong laxative effect that provided welcome relief from their rich, meat-heavy diets. “People who came there took a couple of glasses of the said water – which has a different taste from ordinary water – after which, walking up and down, these had, in our opinion, a very good effect,” reported one satisfied clogged visitor. This was later found to be due to the water’s high content of the mineral magnesium sulphate, also known as Epsom salt.

Four hundred years later, magnesium’s therapeutic properties are being heralded again, and it has been called “the super mineral of the moment” in the press. On social media, I am bombarded with posts about the supposed benefits of taking magnesium supplements, including improved sleep, energy levels, mental clarity, bowel movements, and heart health, as well as reduced muscle pain, anxiety, migraines, and PMS (premenstrual syndrome) symptoms. Confusingly, these supplements come in many different forms. But do they actually work?

There is no doubt that magnesium is vital for our health. It stabilizes and helps the operation of hundreds of enzymes that catalyze important chemical processes in the body. It also provides stability to fundamental molecules such as DNA and ATP (adenosine triphosphate), binds to various receptors and can move in and out of cells. This has given it roles in a wide range of important processes, including energy production in cells, nerve signalling, muscle contractions and heart rhythm regulation.

Nutritionists generally recommend that we try to meet our magnesium needs by eating a mix of healthy foods rather than relying solely on supplements, as these foods come with extra minerals, vitamins and other nutrients. Common sources of magnesium include nuts, seeds, leafy greens, whole grains, legumes, meat, seafood, dark chocolate and beer (some beers are more bitter than others due to extra magnesium in the brewing water). People who get plenty of magnesium from their diets probably won’t benefit from taking a supplement because all the positions for magnesium in their body are already taken, meaning they’ll just remove the excess.

That said, it has become more difficult to get enough magnesium from food. We eat too much processed junk, which has minimal magnesium. In addition, excessive farming has depleted magnesium from our soil, so even fresh fruits, vegetables and whole grains do not contain as much as before. As a result, research suggests that approximately 35 to 50 percent of the population in the UK, US and Australia do not consume enough magnesium.

Some people are also more prone to low magnesium because they have conditions such as celiac disease or Crohn’s disease, which reduce intestinal absorption, or diabetes or alcohol abuse, which increase excretion. When I was pregnant, I had excruciating leg cramps because pregnancy lowers magnesium levels, making it harder for muscles to relax after contraction. Athletes are often deficient as well, since intense, prolonged exercise increases magnesium consumption and also causes it to be lost through sweat. In addition, some medications, including certain immunosuppressants and chemotherapy, are known to deplete magnesium.

Unfortunately, there is no simple test to find out if you have a magnesium deficiency. About 99 percent of magnesium in the body is stored in bone and soft tissue, which means that blood tests do not give a clear picture of total magnesium levels. The gold standard test involves a magnesium infusion followed by a 24-hour urine collection, which is expensive and inconvenient. If minimal magnesium is found in the urine, it points to a deficiency because the body eagerly soaks up magnesium from the infusion rather than draining it because it already has enough.

Symptoms of magnesium deficiency include muscle soreness, fatigue, brain fog, irritability and sleep problems, but of course there are many other things that cause these as well. This makes it easy for magnesium supplement manufacturers to find customers.

The many types of magnesium supplements

Magnesium supplements come in many different forms because they contain salts of magnesium, where the positively charged magnesium must be paired with a negative ion, which can be chosen from a wide variety of options. When magnesium is combined with sulfate in Epsom salt, for example, it draws extra water into the intestines to soften the stool and get things moving. Magnesium oxide and magnesium citrate work in the same way. Other popular supplements pair magnesium with amino acids or other organic compounds that have some shaky evidence of benefits for the brain, muscles or heart. These include magnesium glycinate, L-threonate, malate and taurate. However, it should be noted that when it comes to the amino acids in these supplements, they are also readily available from a healthy diet.

Another option is to rub magnesium cream or spray on the skin or soak in Epsom salt baths, but less magnesium is absorbed this way than when taken as an oral supplement. There is actually some debate as to whether it penetrates the skin at all. This probably explains why rubbing a magnesium cream on your legs during pregnancy didn’t seem to do much for the cramps. It is also unclear whether the proposed muscle relief from Epsom salt baths stems from the magnesium or just the warm water.

I personally don’t take magnesium supplements because I’m not convinced they offer anything more than a sensible diet does, and I like food more than pills. However, there is some evidence that magnesium supplements can help with insomnia and mild anxiety in people who don’t get enough magnesium from their diets. Likewise, there is some evidence that they can reduce muscle soreness in athletes who have higher magnesium needs.

In contrast, there has been no decent research looking at their effects on energy or concentration. Still, if you find that they help with these things, and even if it’s just a placebo effect, there’s no reason to stop taking them because they’re considered relatively safe. Just don’t overdo it like English Lord Richard Evelyn, who died in 1670 after partaking too much in Epsom’s waters. According to his brother, diarist John Evelyn, his demise was caused by “drinking too much Epsom water when in full health, and having no need of it”.