Magnesium for sleep: does it help?

Why might magnesium help sleep?

Magnesium is involved in hundreds of processes in the body, including how nerves and muscles relax. It acts on the same calming brain receptors as some sleep medicines (GABA receptors) and dampens excitatory signals. That makes it plausible that topping up low levels could help sleep. Plausible is not the same as proven, though.

What do the trials show?

There are only a few trials, and they’re small.

• The best-known trial, from Iran in 2012, gave 46 older adults with insomnia either 500 mg of magnesium or a placebo every day for 8 weeks. The magnesium group improved more on insomnia scores and sleep efficiency.
• A 2021 review pooled three trials with 151 older adults. Magnesium cut the time to fall asleep by about 17 minutes compared with placebo. Total sleep rose by about 16 minutes, but that wasn’t statistically significant. The authors rated the evidence low quality and said better trials were needed.

There are no good trials in younger adults, and the people studied may have been low in magnesium to begin with. If your diet already gives you enough, extra magnesium is less likely to help.

Is it safe?

For most healthy adults, yes, at sensible doses. The NHS says taking 400 mg or less a day from supplements is unlikely to cause harm. High doses for a short time can cause diarrhoea.

• Kidney disease: don’t take magnesium supplements without medical advice, because your kidneys may not clear it.
• Medicines: magnesium can reduce how well some antibiotics (tetracyclines, quinolones) and osteoporosis drugs (bisphosphonates) are absorbed. Take them at different times, and ask a pharmacist.

Is it worth trying?

If you are older, eat little in the way of greens, nuts and wholegrains, and want to try a supplement, magnesium is low risk and cheap. Expect a small effect at best. It isn’t a treatment for long-term insomnia, where CBT for insomnia works far better.