How electrolytes can support quality sleep

In my book Wired to Eat, I spend half a chapter on the most important factors influencing sleep including blood sugar management, avoiding tech, and other aspects of sleep hygiene. I don’t, however, speak to the link between various electrolytes and sleep. Today, I’ll expand my focus to cover just that.

You may know of research suggesting magnesium reduces insomnia and enhances sleep quality. This article will cover that science, plus supplementation protocols from those studies. 

But did you know that sodium, potassium, and calcium may influence sleep too? The research is buried under layers of dust — so unless you’re an even bigger electrolyte nerd than me (a rare feat!), you’ll probably learn something new today.

Let’s dust off that research and explore the frontier of electrolytes and sleep.

Magnesium for Sleep: Clinical Evidence

Magnesium is the most researched and most publicized electrolyte for sleep. You’ve probably seen supplement brands hawking magnesium for this reason. It’s not all hype, but we should temper the marketing by reviewing the clinical evidence.

A 2021 BMC meta-analysis included three randomized controlled trials involving 151 older adults with insomnia. Participants received 320–729 mg of magnesium (via magnesium oxide or magnesium citrate) two to three times a day for 20–56 days. Researchers assessed sleep quality by questionnaire, sleep journal, or sleep electroencephalogram (EEG).

Compared to placebo, people taking magnesium fell asleep about 17 minutes faster. They also got 16 more minutes of total sleep, though this result wasn’t statistically significant.

Yet the researchers weren’t too impressed, considering the evidence to be “low to very low quality” and “moderate-to-high risk of bias.” For them, the data was insufficient to strongly recommend magnesium for insomnia, but they did weakly recommend it anyway since it’s cheap and low-risk.

Observational data provides a stronger case for magnesium. In a 2018 study of 1,487 Chinese adults, higher magnesium intakes correlated with a lower likelihood of falling asleep during the day in women, but not in men. Another analysis of 3,964 young Americans found that compared to the bottom quartile, the top quartile of magnesium consumers had “borderline” better sleep quality plus significantly fewer nights of short sleep (<7 hours in a night).

When parsing observational data, it’s crucial to remember that correlation isn’t causation. Magnesium may not cause better sleep. Perhaps high magnesium folks eat healthier overall, enhancing other drivers of sleep quality. There’s a great many potential confounders.

That said, magnesium interacts in the body in a few ways that could impact sleep. Let’s review the mechanistic data now.

Why Magnesium May Improve Sleep

Here are five ways in which magnesium might be able to impact your sleep.

#1: Relaxation

Magnesium has relaxative properties that may improve sleep. These properties likely stem from changes in neurotransmitter activity.

Specifically, magnesium blocks N-methyl-d-aspartate (NMDA) receptors in the brain that are sensitive to an excitatory neurotransmitter called glutamate. Less glutamate, less excitatory brain activity that may keep you awake.

Magnesium also increases levels of GABA, a calming neurotransmitter. More GABA, more relaxation, potentially better sleep.

#2: Circadian rhythm entrainment

The cells in your body operate on a sleep-wake cycle called the circadian rhythm. Proper entrainment of this cycle — synchronizing your snoozes to the ebb and flow of light, food, exercise, and other factors — promotes better sleep.

Magnesium may be one of these other factors. Research suggests this dynamic mineral regulates circadian clocks in plant and animal cells.

#3: Hormonal support

A 2012 randomized controlled trial found that 46 older adults supplementing 500 mg of magnesium per day for eight weeks experienced the following benefits:

• Reduced cortisol, a stress hormone.
• Increased melatonin, a hormone that can improve sleep cycles.
• Increased renin, a hormone linked to better deep sleep.

Additionally, researchers found that the adults benefited from improved sleep time and sleep efficiency. These changes bolster the case for magnesium as a sleep aid.

#4: Reduced muscle cramps

It’s not easy to get back to sleep after waking with a Charley horse. If muscle cramps are what keep you up at night, magnesium may help.

A 2021 randomized controlled trial found that magnesium supplementation (226 mg/day of magnesium oxide) significantly reduced nocturnal leg cramps and improved sleep quality in at-risk patients.

#5: Anti-depressant effects

There’s a three-way link between magnesium, depression, and sleep. Consider that:

• Depressive symptoms may cause poor sleep.
• Poor sleep may cause depressive symptoms.
• Supplemental magnesium may improve both symptoms of depression and poor sleep.

Depression is a complex and multifactorial issue — I’m not saying magnesium will cure it by any means. But if depression is keeping you up at night and magnesium deficiency is a potential contributor, optimizing your magnesium intake is low hanging fruit worth exploring.

Sodium Restriction and Sleep

Beyond magnesium, you don’t hear much about other electrolytes for sleep. That needs to change, especially for sodium.

Underconsuming sodium causes your body to secrete sodium-retention hormones like adrenaline (aka epinephrine) and noradrenaline (aka norepinephrine). Needless to say, these “fight-or-flight” adrenal hormones aren’t great when you want some shut-eye.

A 1983 study found that three days of sodium restriction (under 500 mg/day) increased noradrenaline levels and decreased REM and deep sleep in 10 young men. I wish there were more recent, more extensive studies on sodium and sleep, but this is what we’ve got.

Relatedly, a 2020 Cochrane review did link sodium restriction (~1,500 mg/day) to higher noradrenaline (+27% for almost 900 participants) and adrenaline (+14% for over 300 participants). So there’s plenty of data showing that low-sodium diets boost these hormones. These data provide mechanistic support for the sodium-sleep disturbance link.

Low-sodium diets also reduce antidiuretic hormone (ADH) secretion, a hormone that tells our kidneys to retain water. Less ADH can mean more night-time bathroom visits, potentially disrupting your sleep. In one study, ADH levels fell by 60% in 12 young men after a week of sodium restriction.

Potassium and Sleep

As we descend deeper into the library of electrolytes, we find a little-known 1991 study on potassium and sleep. Let’s review the details.

Nine young men consumed a low-potassium diet (~1,500 mg/day) for two weeks. Researchers then gave some men a potassium supplement (~3,750 mg/day), while the rest received a placebo for a week. This was a crossover study design, so they swapped groups later. The researchers measured sleep via logs and wrist actigraphy, an imperfect technology that relies on movement to determine sleep quality. I’d love to see a similar experiment using better methods than actigraphy, but this is what we have for now.

The key finding was that potassium supplementation increased sleep efficiency (time asleep vs. time in bed) from 89% to 94%. The researchers speculate that potassium may improve the circadian rhythm, leading to more consistent sleep. But since the study was small, actigraphy is imperfect, and the subjects were potassium-depleted to begin the experiment, we should take these findings lightly.

Regardless, there’s no downside to optimizing your potassium intake, and there are plenty of health benefits beyond sleep.

Calcium and Sleep

Like other electrolytes, calcium conducts electrochemical signals in the brain. Researchers believe calcium supports slow-wave brain activity during deep, restorative sleep.

In 412 shift workers, lower serum calcium levels were correlated with longer time to fall asleep and longer total sleep time. While the longer time spent sleeping may seem like a benefit, this may actually be a detriment in disguise. Workers may require more sleep to achieve the same level of rest. Interestingly, these effects did not hold true for non-shift workers, who may be less vulnerable to calcium-dependent sleep disturbances.

Another 2021 observational study found that low dairy intake was linked to depression and poor sleep quality in 1,422 Jordanian college students. One possible mechanism? Calcium, which is found in high quantities in dairy products, helps convert tryptophan (an amino acid from protein) to melatonin. But calcium might not be the critical variable. Dairy contains tryptophan too, so what if dairy eaters sleep better because they consume more tryptophan from milk? This study can’t answer that question.

Electrolytes for Sleep: Practical Thoughts

I’ll leave you with a few practical thoughts on improving sleep. One takeaway is to avoid electrolyte deficiencies: That goes for sodium, potassium, magnesium, calcium, and otherwise. There’s no downside to optimizing your electrolyte status, and it might improve your sleep through various mechanisms.

Research-backed targets are 4–6 grams of sodium, 3.5–5 grams of potassium, 400–600 mg of magnesium, and 1 gram of calcium daily.

If you’re struggling with insomnia, nocturnal leg cramps, or any other sleep issue, consider trying magnesium supplements. While one high-quality trial used 414 mg of magnesium oxide taken twice daily (which is 60% magnesium, i.e. 500 mg magnesium per day), I advise you to avoid magnesium oxide as it can lead to undesirable dashes to the bathroom. You might experiment with slightly lower doses of better-absorbed forms like magnesium citrate or magnesium malate instead.

While this is all very interesting, you cannot forget that electrolytes are just a tiny piece of the puzzle when it comes to sleep. No amount of magnesium will relax you if your bedtime routine includes a frantic check of the email inbox. No electrolyte will help you outsleep your 6th cup of coffee.

Approach your sleep hygiene holistically — a consistent schedule, a relaxing bedtime routine (I see you, 2 am reader!), limited caffeine intake, and other healthy habits are your path to a good night’s rest. Sleep well!