Magnesium is one of the most well-known minerals in dietary supplements. It is particularly often taken in the evening – with the hope of calming down and sleeping more restfully.
But is there actually scientific evidence for this?
A randomized, double-blind, placebo-controlled human study published in 2025 investigated precisely this question – and explicitly used magnesium bisglycinate.
What is Magnesium Bisglycinate?
In magnesium bisglycinate, magnesium is bound to the amino acid glycine. This makes it a so-called chelate compound.
Magnesium itself is a vital mineral and performs numerous functions in the body. Among other things, magnesium contributes to
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normal functioning of the nervous system,
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normal muscle function,
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normal energy metabolism, and
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the reduction of tiredness and fatigue.
However, the new study went a step further and specifically investigated the connection between magnesium bisglycinate and subjective sleep problems.
The Study: 155 Adults with Poor Sleep
The study involved 155 healthy adults aged between 18 and 65 who reported poor sleep quality themselves.
The participants were randomly divided into two groups:
Magnesium group:
250 mg elemental magnesium as magnesium bisglycinate daily
Placebo group:
identical-looking capsules without magnesium
The intake took place over four weeks. Neither the participants nor the investigators knew during the study who received magnesium and who received placebo.
Thus, the study meets important quality criteria of a modern clinical intervention study.
What were the results?
To assess sleep problems, the scientists used the Insomnia Severity Index (ISI). This established questionnaire records, among other things, difficulties falling asleep, staying asleep, and the subjective impairment caused by sleep problems.
After four weeks, the ISI score decreased:
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by 3.9 points under magnesium bisglycinate
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by 2.3 points under placebo
The difference between the two groups was statistically significant.
This means that while the placebo group also reported improvements, the reduction in sleep problems was greater with magnesium bisglycinate.
A positive effect – but not a sleeping pill
The scientists themselves rated the effect as moderate. However, the statistical effect size was Cohen's d = 0.2.
This is an important classification.
The study does not show that magnesium bisglycinate is a sleeping pill or can treat sleep disorders. Rather, it provides controlled human study evidence that taking magnesium bisglycinate in adults with subjectively poor sleep could have an additional effect on perceived sleep problems.
Particularly interesting: Magnesium supply could play a role
An exploratory analysis of the study showed another interesting point:
Participants whose dietary magnesium intake was lower at the beginning seemed to respond more strongly to supplementation.
This is biologically plausible and could explain why people report very different experiences with magnesium.
Those who already consume enough magnesium through their diet may benefit less from additional supplementation than someone with low magnesium intake.
However, the authors point out that this finding was initially only exploratory and needs to be confirmed in further studies.
Why is this study particularly interesting?
Magnesium and sleep have been scientifically studied before. The problem: Many older studies were small, used different magnesium compounds, or investigated specific groups of people.
A previous systematic review, for example, found evidence of reduced sleep latency in older adults but considered the available evidence limited due to the small number and quality of studies.
The new study is therefore interesting because it:
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was randomized,
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was double-blind,
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had a placebo group,
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included 155 participants, and
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specifically investigated magnesium bisglycinate .
This provides much more concrete information on this specific form of magnesium.
What the study does not yet answer
This study also has limitations.
The study duration was only four weeks. In addition, sleep was assessed primarily using questionnaires.
Objective sleep measurements – for example, by means of polysomnography in a sleep laboratory – were not part of the study. The authors therefore explicitly recommend longer investigations and additional objective sleep parameters.
It also remains unclear which people particularly benefit from magnesium bisglycinate and what role an actual magnesium deficiency plays in this.
VitaRex Magnesium Bisglycinate: 300 mg daily
Our VitaRex Magnesium Bisglycinate provides 300 mg elemental magnesium with two capsules daily.
This daily dose is very close to the 250 mg magnesium used in the described human study.
The VitaRex product contains:
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300 mg magnesium per daily dose
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Magnesium in the form of magnesium bisglycinate
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only 2 capsules daily
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120 capsules per container
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vegan capsule shells
Magnesium has been proven to contribute to the normal function of the nervous system and muscles, as well as to the reduction of tiredness and fatigue.
Conclusion
The new human study provides interesting clinical data for magnesium bisglycinate.
After four weeks, adults with poor sleep quality reported a slightly greater improvement in their sleep problems under 250 mg magnesium as bisglycinate than under placebo.
The effect was small but statistically significant. Particularly interesting is the indication that people with lower magnesium intake may benefit more.
Thus, the study provides another building block for understanding the role of magnesium – and at the same time shows why, with dietary supplements, not only the mineral itself but also the magnesium form, dosage, and initial supply should be considered.
Source
Schuster J. et al. Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial. Nature and Science of Sleep, 2025.
