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Magnesium Supplements for Sleep May Not Work Like a Dream

It’s easy to hypothesize how magnesium supplements might improve sleep. But do they really?

Everywhere I turn these days, an influencer is trying to sell me magnesium supplements. Apparently, all of us who find it difficult to fall asleep and stay asleep all night are missing the boat. The answer is a simple mineral available as a dietary supplement: the all-mighty magnesium.

If this endorsement turns out to be a bit iffy, it won’t be the first time. When podcasts and YouTube videos were recognized as potentially lucrative platforms for marketers, we started to see our favourite content creators, trying to eke out a living on the Internet, take on sponsorships for brands we had never heard of before. I remember a particular watch, a darling of podcasters and YouTubers, which was later denounced as a cheap Chinese watch you could buy for a fraction of the price on the e-commerce platform Alibaba. Then there were those “premium Japanese knives.” One YouTuber, who worked as a kitchen cook, later regretted partnering with them. The knives were his least favourite but his viewers, knowing his background, were bound to think that his endorsement meant the knives were first rate.

And who could forget the uproar over Established Titles, a purchasable certificate which was said to grant you the legal right to call yourself a lord or lady by buying a tiny piece of Scottish land? It turned out to be little more than a gag gift, and many influencers lost face for endorsing what was referred to as a scam.

Now, one the hottest items sponsoring YouTube videos is magnesium supplements. Will they stop you from lying wide awake in bed at night? Or is this another scam?

Inadequacy versus deficiency

It makes sense that magnesium would be eyed by the dietary supplement industry. This mineral is used by our body in over 300 different enzymatic reactions. It helps us synthesize DNA, RNA, and proteins. It facilitates the contraction of our muscles. It plays a part in controlling our blood glucose levels.

It is a magnificent, electrically charged jack of all trades.

Unfortunately, despite its necessity to bodily functions, it is often reported that many of us are not getting enough magnesium from our food, putting us at risk for insomnia and a host of health problems. The truth is a tad more complicated. Assessing how much magnesium people are ingesting is commonly done in one of two ways. Researchers can ask a person about the food they are eating and calculate approximately how much magnesium they are ingesting. This is how we know, for example, that somewhere between two-thirds and three-quarters of Americans fall short of the recommended daily allowance of magnesium. Food questionnaires, however, are known to be quite unreliable, so these estimates have to be taken with a grain of salt.

The second way is to look at how much magnesium is present in the blood, but that can be deceiving. The body of a 70-kg (154-lb) person contains roughly 25 grams of magnesium, with a little over half stored in bones, a little under half stored in muscles and soft tissues, and a tiny amount, less than 1%, in circulation in the blood. The problem is that blood levels can be normal and a person still be significantly deficient in magnesium, because magnesium can be released from bones to preserve normal blood levels.

Having said that, there is an important difference between magnesium inadequacy and magnesium deficiency. Many of us who do not consume enough magnesium in our diet appear not to suffer for it. But as we veer from inadequacy to deficiency, we start to see symptoms like loss of appetite, fatigue, nausea, and vomiting. At the dramatic end of the spectrum, we can end up in a state of hypomagnesemia, which manifests as tremors, cardiac arrhythmias, and abnormally low levels of calcium and potassium in the body.

Some have argued that, while relatively low levels of magnesium might appear to be benign, it is possible that they cause or worsen common conditions such as insomnia. Quality sleep, so important to our health, evades many of us. Half of all Canadians report having trouble falling asleep or staying asleep, and over a decade ago it was estimated that nearly one in seven met the criteria for insomnia. Is the answer simply for us to pop a magnesium tablet once a day?

Magnified data of low magnitude

The problem is that, right now, science can’t settle the question. The trials are far and few in between and the quality of the evidence is poor. And it’s not from a lack of trying on the part of the industry, which would love to be able to point to studies while they sell you magnesium tablets: many such industry-funded studies are out there. It’s just that they are either not dressed to impress or they come to contradictory conclusions.

A systematic review and meta-analysis of clinical trials investigating whether magnesium supplementation benefits older adults with insomnia tracked down only three studies, one of which was conducted using a meager 12 participants. The authors of this review concluded that the trials had a moderate-to-high risk of bias and that the quality of the evidence went from low to very low. They called this literature “substandard,” such that doctors couldn’t use it to make a good recommendation either way. Another important issue is that study participants don’t simply start taking magnesium supplements; they are part of a trial in which their sleep is assessed and have to visit a clinic, keep a sleep diary, and often are told to stay away from stimulants and keep to a predetermined sleep time. Is the magnesium really helping or is this all due to increased attention to sleep hygiene?

The data on the ground is so thin it’s see-through, but that hasn’t stopped researchers from coming up with plausible ways in which magnesium could influence sleep if it did. It’s an easy and common enough proclivity: there are so many molecules in our body in so many arrangements, tied to so many molecular cascades of events, that like the conspiracy theorist wrapping red yarn around pins on a board, the hopeful molecular biologist can easily trace a path from magnesium to sleep. It turns out that magnesium can bind to and either activate or dampen important neurological receptors in our body which have a role to play in sleep. Fluctuating levels of magnesium in the body can also impact how much hormones we produce, like melatonin (the sleep hormone) and cortisol (the stress hormone). But coming up with a mechanism of action is no replacement for actually showing that supplementation improves sleep.

There are other possible mechanisms that bind magnesium to sleep: the roles it plays in restless leg syndrome and in muscle cramps, both of which can tarnish our sleep. And studies have been conducted to see if supplementing a patient with magnesium reduces restless leg syndrome or cramps. A 2014 review of the evidence on nocturnal leg cramps concluded that magnesium supplements do not appear to be effective in the general population, but may have a small effect in pregnant women, although the studies were small, with short follow-ups, and they used different doses of magnesium supplements, making comparisons hard. As for restless leg syndrome, I found one Iranian trial that gave groups of 25 participants either magnesium, vitamin B6, or a placebo. The doctors and researchers knew which group received which pill—a lack of proper blinding which can influence the analysis—and all three groups benefitted in terms of fewer symptoms and improved sleep, with the magnesium and vitamin B6 groups improving more than the placebo group. It is hard to conclude anything from this single study.

Many of the studies I read on this topic exemplify the allergy that scientists have to reporting negative findings. The data needs to be tortured and its analyses looked at with rose-tinted glasses to extract some hope of a benefit, often highlighted in the paper’s abstract, while the harsh reality can be found in the graphs and tables a few pages downstream. Sleep improvement, for example, is not just reported as an average for everyone tested; it’s also given a confidence interval, the full range where the true value is thought to be found. A couple of papers had confidence intervals so large you could drive an eighteen-wheeler through them. Yet these ho-hum results were spun by the authors as proof that supplementing with magnesium (often in combination with other nutrients) did improve sleep.

The bottom line is that there is no good evidence that supplementing with magnesium will improve your sleep. There are only mechanistic inferences and anecdotes. Many experts, faced with this paucity of data, will conclude that these supplements are cheap enough that they are worth trying if you are sleep deprived. A few caveats. Our diet can be tweaked to include more magnesium: sources high in the mineral include pumpkin seeds, almonds, spinach, and potatoes. Insomnia can be caused by many things, and ruling out important diagnoses shouldn’t be skipped in lieu of visiting the dietary supplement aisle at your local drugstore.

Also, magnesium isn’t sold on its own: it has to be bound to something. You can buy magnesium oxide, magnesium citrate, magnesium chloride, even milk of magnesia, which is magnesium hydroxide and is commonly used as an antacid in low doses and as a laxative in higher doses. In fact, magnesium supplements can cause gastrointestinal upset, including diarrhea. If you are interested in getting the form of magnesium that is better absorbed by the body, small studies have reported that magnesium citrate, aspartate and lactate are superior to magnesium oxide and sulfate in this regard. Keep in mind that dietary supplements like magnesium are not regulated as stringently as pharmaceuticals, and contaminations and adulterations are not unheard of.

And finally, yes, taking a magnesium supplement may cure your insomnia, but it may be because that insomnia would have resolved itself anyway. Acute episodes of insomnia are temporary and often resolve when the trigger—stress, illness, life changes and medication adjustments—is eliminated. Seeing a resolution of symptoms after supplementation is no proof that it worked. That’s why we do randomized controlled trials. But in the case of magnesium for sleep, I can only dream we had better ones.

As for influencers endorsing magnesium supplements, keep in mind that they are unlikely to dive deeply into the scientific literature before accepting a sponsorship for a health product. Corporations want to sell you goods. Influencers want to pay the rent. It’s up to consumers, unfortunately, to not fall asleep at the wheel and ask the right questions before whipping out their credit card.

Take-home message:
- Magnesium is a mineral which plays important roles in the body, including participating in over 300 enzymatic reactions
- There is currently no good scientific evidence that taking magnesium supplements will improve your sleep


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