Supplement capsules on a plain background

Magnesium Glycinate Sleep Benefit Real but Small, Studies Show

magnesium glycinate is one of the UK's best-selling supplement forms, marketed heavily on claims that it improves sleep. A review published by AOL on 12 August 2026 examined the evidence behind those claims and found a genuine but modest effect, smaller than most marketing suggests. The review's most recent citation, a randomised, placebo-controlled trial published in Nature and Science of Sleep in 2025, gave 155 adults with self-reported poor sleep either 250mg of elemental magnesium as magnesium bisglycinate or a placebo capsule for four weeks. Insomnia Severity Index scores fell by 3.9 points in the magnesium group compared with 2.3 points on placebo, a difference the trial authors called barely statistically significant, with a p-value of 0.049 and a small effect size, Cohen's d of 0.2. The benefit was concentrated in participants who started with low dietary magnesium intake. The trial's lead author, Adrian Lopresti, discloses a role at a contract research organisation that receives funding from nutraceutical companies.

What the older evidence shows

A 2021 meta-analysis in BMC Complementary Medicine and Therapies pooled three randomised trials in 151 older adults and found people fell asleep about 17 minutes faster on magnesium than on placebo, but rated the underlying evidence "low to very low quality." A 2023 systematic review covering nine studies and more than 7,500 adults found consistent observational links between magnesium status and sleep, but contradictory results once studies moved to randomised designs. Across all three reviews, the pattern is the same: an association that shows up reliably in observational data softens, but does not disappear, when tested in controlled trials.

What this means for your supplement routine

None of the trials reviewed found magnesium glycinate resolves insomnia; the consistent finding is a small improvement, most evident in people whose diet is already low in magnesium. Readers comparing sleep products against marketing claims may find it useful to know what the underlying trials actually measured rather than the headline they were sold on. Perqen's health and wellness range lists a broad set of vitamin and mineral products people research alongside claims like these, though no specific product was assessed in the studies above.

How Perqen members save

Perqen members pay £4.99 a month or £29.99 a year for member pricing across all 1,393 products in stock, sourced through PowerBody, an authorised EU distributor. Full membership pricing details are published on the site.

This article reports published news and research and is for information only. Food supplements are not a substitute for a varied diet or medical care, and no product mentioned is intended to diagnose, treat, cure or prevent any disease. Speak to your GP or pharmacist before changing what you take, especially if you are pregnant, breastfeeding, or taking prescribed medicines.

Sources

Originally reported by AOL. This article has been reviewed by Dr Tosin.

Related on Perqen

Back to blog