Does Magnesium Help You Sleep?

If you’ve been hunting for ways to improve your sleep, you’ve probably seen adverts claiming that magnesium supplements could be the answer… But is there any evidence to support those claims? Does magnesium help you sleep? In this post we’ll explore what magnesium does in the body, foods that contain magnesium, why some people are at risk of deficiency, and what the research says about magnesium and sleep.

Why is magnesium important in the body?

Magnesium is a mineral which helps to support a huge range of functions in the brain and body.

• It helps maintain the normal function of our cells, enabling energy production, protein synthesis, DNA repair and replication, and reduces oxidative stress.
• It’s built into the infrastructure of bones and teeth.
• It enables nerve conduction and neurotransmitter synthesis, which supports learning and memory.
• It helps to moderate our stress response.
• It helps maintain healthy blood sugar levels.
• It keeps the heart beating regularly.
• It supports the immune system, and decreases harmful inflammation.

A lack of magnesium is a risk factor for the development and progression of many chronic illnesses including diabetes, heart disease, high blood pressure, osteoporosis, and dementia.

Do you get enough magnesium in your diet?

We all need Magnesium - the body can’t make it - we rely on what we eat. The good news is that magnesium is found in a lot of foods. Rich sources include most foods with high fibre content:

• Leafy vegetables
• Legumes or pulses
• Nuts
• Seeds
• Avocados
• Bananas, kiwis
• Whole grains
• Fish and meat

It’s also added to some cereals and mineral waters.

Recommendations for how much magnesium we need vary by country, but as a minimum, it’s around 5 to 7mg/ kg of body weight - so at least 300mg per day for women, 400mg for men.

We store around 25g of magnesium in the body at any one time -

• 50-60% is in our bones and teeth
• 30% in our muscles
• And 10-20% in the brain and other tissues

Only a tiny fraction - <1% - will be detectable in the blood as serum magnesium.

What happens if we consume too much magnesium?

The body is very good at balancing our intake of magnesium with the amount we excrete. Any magnesium we don’t need is filtered out by the kidneys and excreted in our urine. If you’re generally healthy, it’s highly unlikely that you will suffer from hypermagnesemia, or too much magnesium. It may happen in kidney failure, however, and signs include weakness, confusion, low breathing rate, poor reflexes and cardiac arrest.

What causes magnesium deficiency?

Low levels of magnesium can be caused by eating too little, not absorbing enough, or excreting too much. If you persistently eat a diet which is low in fibre and high in ultra processed foods, over time, this will put you at greater risk of magnesium deficiency.

Chronic conditions such as diabetes, GI disorders and kidney problems will often upset the magnesium balance by unhelpfully altering absorption or excretion.

Other factors that can lower magnesium retention include:

• Diets unusually high in sodium, calcium or protein
• Excessive caffeine, or alcohol - or both,
• Drugs including diuretics, antacids and antibiotics
• Pregnancy
• Menopause
• Older age
• Stress

Being exposed to any kind of chronic stressor may reduce our magnesium reservoir.

A stressor is anything which fires up our fight or flight stress response - unleashing the physiological cascade which includes adrenaline, and cortisol, and is designed to prepare us for action.

Exposure to many different types of stressors - exams, noise, cold, and lack of sleep has been found to increase the rate of excretion of magnesium into the urine. Over time, chronic exposure to stress could increase the risk of magnesium deficiency.

Magnesium is also involved in managing our response to stress. We need magnesium for the production of serotonin, and to activate calming GABA receptors, and to reduce cortisol levels.

So, if chronic stress lowers our stress-busting magnesium reserves, there is potential for a vicious cycle, where the magnesium-deprived brain and body is then more susceptible to the damaging effects of stress. Low magnesium levels have been linked to depression, anxiety and other mental health disorders.

How do you know if your magnesium levels are low?

Only 0.3% of the body’s magnesium is in the serum. The vast majority of it is in the bones and tissues. Our bodies work so hard to maintain blood levels within a narrow window (0.7–1 mmol/L), using the body’s stores as a buffer, that you could have apparently healthy levels in a blood test, which still mask a magnesium deficiency. For this reason, research studies will use food diaries over several days to estimate dietary magnesium intake.

If you eat a broadly healthy diet, with plenty of whole foods, and you don’t have any GI or kidney issues, you’ve probably got a hearty store of magnesium.

Large scale studies suggest anything from 10 to 60% of the general population are not getting enough magnesium in their diet, depending on the country. In the UK, young people, the elderly, those from more deprived backgrounds and those with chronic conditions are at greatest risk of magnesium deficiency.

What are the symptoms of magnesium deficiency?

Unfortunately, the symptoms of low magnesium are fairly non-specific, and can easily be confused for chronic stress. Here are some of the symptoms of a magnesium deficiency:

• tiredness
• irritability
• anxiety or nervousness
• GI spasms
• muscle cramps
• headaches
• mild sleep problems

Will taking a magnesium supplement improve your sleep?

If you’ve read any of my other blog posts, you’ll know that there are 3 major systems which influence your sleep quality. In a nutshell, we need consistency to strengthen our circadian rhythms, we want to build up sleep pressure without letting stimulants interfere, and we need to convince the stress system that it’s safe to switch off.

Magnesium potentially has multiple soothing effects on the stress system, but it’s likely that a supplement will only help if you’re correcting a magnesium deficiency, and it could take a few weeks.

If you’ve noticed an immediate overnight benefit from a magnesium supplement, it may be because of the ‘placebo effect’. If you believe something will help you sleep, your anxiety about not being able to sleep reduces, and you fall asleep faster, and stay asleep for longer. This isn’t necessarily a problem, but it doesn’t tell us whether magnesium is the active ingredient.

To be confident that magnesium improves sleep, we need to compare magnesium to a placebo, in a randomized controlled trial.

What is the evidence that magnesium can help with sleep?

A meta-analysis published in 2021 combined the results of 3 small trials in 151 adults aged 55 or above. They found that on average magnesium helped people fall asleep 17 minutes faster, but didn’t have consistent effects on sleep quality or total sleep time (Mah et al 2021).

One study that is often used as evidence that magnesium helps people sleep better gave 46 adults over 60 years of age 500mg of magnesium, as magnesium oxide, for 8 weeks, compared to placebo (Abbasi et al 2012). Although they fell asleep faster after 8 weeks, they still took over an hour to fall asleep at the end of the trial. Sleep quality improved by 2 points on the Insomnia Severity Index; a change of 6 points would usually be recognised as a clinically significant improvement In other words, magnesium improved sleep a bit, but not much.

A more recent review explored the effects of magnesium supplements on self-reported anxiety and sleep quality. They found that 5 out of 8 studies reported sleep improvements, 2 studies found no improvements and 1 had mixed results (Rawji et al 2024).

Does magnesium threonate help with sleep?

Recently on social media, magnesium threonate has been championed for sleep. There is only one placebo-randomised controlled trial which has assessed the effects of magnesium threonate (Hausenblas 2024, forthcoming). Adults aged 35-55 took 1.0g of magnesium threonate for 3 weeks. Although there were a handful of significant effects, suggesting slightly more restorative sleep in the intervention group, the majority of sleep metrics were not different between the supplement and placebo groups. There were no differences in overall sleep score using an Oura wearable sleep tracker.

Are there side effects of taking magnesium supplements?

The most frequent downside of some magnesium supplements is laxative effects or diarrhoea, but this is thought to be more of a problem with magnesium sulphate, citrate or oxide.

In conclusion? Is it worth buying a magnesium supplement to improve your sleep?

The evidence for magnesium supplementation for sleep is favourable, but does not support a strong effect. If you are at risk of magnesium deficiency - for example, you have diabetes, you eat a low fibre diet, you’re over the age of 55, or you are really struggling with my sleep, there is potential that it might help your sleep a little bit. For most healthy people, the evidence suggests that you may not notice a change in your sleep.

However, magnesium does have an array of benefits beyond sleep. It is indispensable for skeletal muscle integrity, energy production, limiting inflammation and protecting brain cells from oxidative stress.

So, regardless of the effect on your sleep, it might be worth considering a supplement as an insurance policy if you are concerned that you are not getting enough from your diet.

As for all dietary supplements, please check in with your doctor or medical team that it is suitable for you before you buy it. I would recommend keeping a sleep diary before you start taking it, so that you track whether or not it has an impact on your sleep.