Of the many tasks that magnesium has, it is its role in helping us to sleep better that regularly comes up as a reason to take magnesium supplements. In this blog post, I’ll look at the latest evidence for magnesium and sleep. I’ll also profile the main food sources of magnesium and critique the merits of the many different supplemental forms of magnesium.
Magnesium is an essential mineral. You have about 30 grams of it in your body with half of this in the bones. Much of the rest of the body’s magnesium is found in the muscles and soft tissues. Only 1 percent is found in the extracellular fluid where it serves as an electrolyte. As an electrolyte, it helps to maintain fluid balance.
What else does magnesium do? It is a cofactor for hundreds of enzymes involved in many metabolic pathways. These include energy production, nucleic acid and protein synthesis, and cell signalling. And together with calcium, magnesium is involved in muscle contraction and blood clotting. That’s a lot of work for one mineral.
There are many health conditions linked to magnesium – or at least a deficiency of magnesium. These include heart disease and high blood pressure, diabetes and muscle cramping. I’ve already written a blog post on this topic so you can check that out here. For this post, I want to focus on one health area that magnesium is thought to be involved in: and that’s sleep quality.
Magnesium and sleep quality
To fall asleep and stay asleep, we need to be relaxed both physically and mentally. That’s obvious. Magnesium may help with this process by activating the parasympathetic nervous system which is the system responsible for getting you calm and relaxed. It does this through various neural and hormonal systems. These systems include neurotransmitters and regulation of the hormone melatonin, which guides the sleep-wake cycle in your body.
That all sounds good in theory, but can a magnesium supplement get you to sleep quicker and keep you asleep outside of any placebo effect it can have? You would think with the amount of advice you hear and read to take magnesium for good sleep quality, there should be lots of scientific evidence to support it. You have thought wrong.
The latest research
Despite a lot of research looking at the question of magnesium and sleep (which can be very mixed in their findings), there haven’t been a lot of critical reviews bringing together all the research in one place. That was the purpose of a systematic review published in 2022.
The review analysed the results from 9 research studies involving over 7,000 participants to determine whether a person’s magnesium status is associated with sleep quality. And importantly: the research team also explored if magnesium supplementation had a positive benefit in controlled trials that used a placebo.
And here were the findings. For observational studies looking at dietary magnesium and sleep quality, there did appear to be a positive link with an association between higher magnesium intake (from diet and supplements) and better sleep quality. That’s all nice, but these were observational studies. So, there could be other unknown factors explaining the link that were not related to magnesium.
Let’s look at the ‘gold standard’ trials covered in the review. And these were randomised-controlled trials where people were given either magnesium supplements or a placebo without knowing which was which. It is important to do the studies like this because if you give someone a pill and tell them it could help them sleep better then guess what could happen? Their mind can run with this and help relax the person into a deeper sleep. Even if it was just a placebo pill.
So, what do the randomised-controlled trials have to say? Agreeing with my prior view when I’ve looked at this research field before, the results were….mixed and inconsistent.
One study with 46 older participants who took 500 milligrams of magnesium or a placebo for 8 weeks found that magnesium supplementation increased sleep time and sleep efficiency. But the other 4 controlled trials examined in the review did not produce statistically significant improvements in sleep outcomes.
None of this means there wasn’t any benefit of magnesium on sleep. Only that it was pretty hard to see it which brings in the question of if any benefits were of clinical significance and noticeable to the person.
But, before dismissing the research be aware that these studies represent the averages of everyone in the trials. And as human beings, our responses will be variable. Some people did benefit in the studies, but it also means that someone people did worse.
What the research is saying to me is that the benefit of magnesium on sleep, if it is really there, is likely small. But the research field is pretty modest so one shouldn’t dismiss it or endorse it one way or another.
But outside of the world of clinical trials, perhaps there can still be a benefit. And here we are talking about the powerful placebo effect. And if I’m lying awake struggling with insomnia then I’d happily take a cheap magnesium placebo pill if I believed it would get me to sleep quicker. Because if you believe in it, well, it may just work. And that is after all part of the mind and body relaxation response that gets us off to sleep in the first place.
Magnesium from foods first
If magnesium does have some role in sleep quality, then before you turn to a supplement, let’s have a look at diet first. While there are many food sources of magnesium, no one food source stands out as the ‘go-to’ food. Even the best food sources of magnesium tend to only meet about one-fifth of what a person needs each day.
Even the best food sources of magnesium tend to only meet about one-fifth of what a person needs each day.
Since magnesium is part of chlorophyll, green leafy vegetables are good sources with spinach being one of the best sources. Wholegrains and nuts such as almonds also have good amounts of magnesium in them. Meats and milk have an intermediate content of magnesium. Highly refined foods generally have the lowest.
So the key to getting plenty of magnesium in your diet is having a diversity of different foods with most of these foods not overly processed.
Even with an adequate diet, some people are at increased risk of magnesium deficiency. These include people with digestive disorders, such as coeliac disease and chronic diarrhoea.
In the short term, not getting enough magnesium in your diet does not produce obvious symptoms. Low magnesium intake over a long time can lead to magnesium deficiency. Symptoms of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. Extreme magnesium deficiency can cause numbness, tingling, muscle cramps, seizures, and an abnormal heart rhythm.
Magnesium supplements: what to look for
So, what about magnesium supplements? There are many different formulations to choose from if you’re thinking of trialling a magnesium supplement to help with sleep.
There are several forms of magnesium supplements available. These include magnesium citrate, magnesium glycinate, magnesium oxide, magnesium gluconate and magnesium chloride. Each form has different absorption rates and potential side effects.
Magnesium citrate and magnesium glycinate are considered to be the most bioavailable and well-tolerated forms. A standard dose for magnesium supplementation is in the range of 200 to 400 mg per day.
Gastrointestinal side-effects, like diarrhoea and bloating, are more common with magnesium oxide or magnesium chloride due to the lower absorption rates of these two forms. That is why magnesium oxide tends to be used as a laxative. Magnesium chloride is easily absorbed orally and used to treat heartburn, constipation, and low magnesium levels.
In general, magnesium citrate is a good choice for supplementation. And it is the most commonly used form of magnesium due to its high water solubility and bioavailability at around 25 to 30 percent. Magnesium bound to amino acids as a chelate such as magnesium aspartate also shows good levels of bioavailability but tends to be a bit lower than magnesium citrate.