Supplement
Magnesium
Mineral · Glycinate / Citrate / Malate / Threonate
Magnesium is a cofactor in more than 300 enzyme reactions – this biochemical role is undisputed, and in a double-blind study with 155 participants the Insomnia Severity Index fell more than under placebo (p = 0.049). For the advertised uses, limitations remain: two controlled analyses missed the primary endpoint for calf cramps, and the sleep finding comes solely from a questionnaire, with an effect size of d = 0.2.
What magnesium is
Magnesium is an essential mineral involved in more than 300 enzyme reactions. Food sources include pumpkin seeds, almonds, spinach, dark chocolate and avocado. As a food supplement it is sold in various salt forms, including glycinate, citrate, malate, threonate and the poorly absorbed oxide.
In the BK-Score it gets 7 out of 10 points for human evidence and 10 out of 10 for track record of use. The track-record axis only measures how widely and how long something has been used in humans – not whether it works.
How it works
As a cofactor of hundreds of enzymes, magnesium is involved in, among other things, ATP production, muscle function and nerve signal transmission. This chain of action is well understood and scores 8 out of 10 points in the BK-Score.
The mechanism explains why magnesium is marketed for cramps and sleep. But it does not replace proof of efficacy: this is where plausibility and study results diverge.
What is well supported
- A significant sleep finding from a double-blind study. In Schuster 2025, the Insomnia Severity Index fell by 3.9 points (−5.8 to −2.0) under 250 mg of elemental magnesium compared with 2.3 points under placebo (−4.1 to −0.4), p = 0.049. 155 participants, four weeks, double-blind. The effect size of d = 0.2 is small, and it was measured by questionnaire.
- The biochemical role is undisputed. Magnesium is a cofactor in more than 300 enzyme reactions and is thus involved in ATP production, muscle function and nerve signal transmission. In the BK-Score, mechanism gets 8 out of 10 points and track record of use 10 out of 10.
- An officially derived maximum level and a known dose threshold. The BfR proposes 250 mg per daily dose in food supplements, based on the tolerable upper limit of 250 mg of additional intake (SCF 2001). The amount at which the typical side effect appears is also quantified: mild diarrhea from around 360 to 365 mg of additional intake.
What the studies show
Cochrane review: primary endpoint for calf cramps missed
Garrison 2020 analyzed 11 RCTs with 735 participants for Cochrane. The main analysis covered idiopathic, mostly nocturnal calf cramps in people aged 61.6 to 69.3 over four weeks. The primary endpoint, the percentage change in cramps per week, was not reached: mean difference −9.59 % (−23.14 to +3.97), moderate certainty of evidence. Cramps per week (−0.18; −0.84 to +0.49) and the proportion with at least a 25 % reduction (RR 1.04; 0.84 to 1.29, high certainty) also showed no effect.
New RCT: compression stockings worked, magnesium did not
Kuusipalo 2026 ran a three-arm multicenter randomized trial with 121 enrolled participants (109 completers) aged 50 to 85 with at least two cramps per week, with four weeks of use and the endpoint at week 8. The primary endpoint, cramp frequency, was not reached for magnesium: adjusted mean difference −0.20 per week (−1.49 to +1.09; p = 0.929). The third arm provides the contrast: compression stockings reduced the frequency by 1.43 per week (−2.36 to −0.50; p = 0.001).
Sleep: small effect, questionnaire only
Schuster 2025 studied, in a double-blind RCT, 155 people aged 18 to 65 with self-reported poor sleep who received 250 mg of elemental magnesium as bisglycinate for four weeks. The Insomnia Severity Index fell by 3.9 points (−5.8 to −2.0) compared with 2.3 under placebo (−4.1 to −0.4), p = 0.049, with an effect size of d = 0.2. It was measured solely by questionnaire. A review by Lopresti 2026 of 12 RCTs rates the evidence as low to very low and makes no routine recommendation for insomnia.
Where the data stop
- Effect on exercise-associated cramps. The Cochrane review found zero randomized controlled trials on this. So there is no negative finding here, but no finding at all – the use is widely advertised nonetheless.
- Objectively better sleep. The significant finding from Schuster 2025 comes from a questionnaire. Neither actigraphy nor polysomnography was used, and the effect size of d = 0.2 is small.
- Superiority of individual salt forms. Glycinate, citrate, malate and threonate are marketed with clearly separated areas of use. Comparative study data supporting this assignment are not available to a corresponding extent; in the BK-Score this costs points on the hype gap.
Status, approval and legal
The German Federal Institute for Risk Assessment (BfR) proposes a maximum level of 250 mg per daily dose for food supplements. It is based on the value of 250 mg of additional intake that the Scientific Committee on Food (SCF) set as the tolerable upper limit in 2001.
Safety
Mild diarrhea occurs from about 360 to 365 mg of additional intake. In the Cochrane review, mild side effects were more frequent under magnesium (RR 1.51; 0.98 to 2.33), mainly diarrhea at up to 37 % compared with 14 % under placebo. Caution is advised in severe kidney failure. This text is for information and does not replace medical advice.
BK-Score Supported, with caveats
| Human evidence | 7 | |
|---|---|---|
| Mechanism | 8 | |
| Safety data | 9 | |
| Hype gap | 6 | |
| Track record of use | 10 |
Biochemically very well supported as a cofactor of hundreds of enzymes, with solid studies on blood pressure and sleep quality, but few large outcome studies. Safety is well studied; the marketing of individual salt forms goes beyond the comparative data.
The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless. “Track record of use 9” means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)
Frequently asked questions about magnesium
How does magnesium work?
Magnesium is a cofactor in more than 300 enzyme reactions and is involved in, among other things, ATP production, muscle function and nerve signal transmission. This biochemical chain of action is well supported. However, it only explains why magnesium is marketed for cramps and sleep, and it does not replace proof of efficacy in controlled studies.
Does magnesium help with nighttime calf cramps?
According to the data reviewed, no. A 2020 Cochrane review with 11 studies and 735 participants missed the primary endpoint, the percentage change in cramps per week. A 2026 multicenter study with 121 enrolled participants confirmed this: the difference from placebo was 0.20 cramps per week, with a p-value of 0.929.
Does magnesium help with muscle cramps during exercise?
There is no evidence for this. The Cochrane review found zero randomized controlled trials on exercise-associated cramps. That is not a negative result but the absence of any reliable investigation. The existing data concern only idiopathic, mostly nocturnal calf cramps in older people, and even there no effect was found.
Does magnesium help you sleep?
The effect is small and weakly measured. In a double-blind study with 155 people, the Insomnia Severity Index fell by 3.9 points compared with 2.3 under placebo, with a p-value of 0.049 and an effect size of 0.2. It was measured by questionnaire only. A review of twelve studies rates the evidence as low to very low.
How much magnesium is allowed in food supplements?
The German Federal Institute for Risk Assessment proposes a maximum level of 250 milligrams per daily dose. This value corresponds to the tolerable upper limit for additional intake set by the Scientific Committee on Food in 2001. It is a proposal for product formulation, not an intake recommendation.
What side effects does magnesium have?
The most common is diarrhea. Mild diarrhea occurs from about 360 to 365 milligrams of additional intake; in the Cochrane review the rate under magnesium was up to 37 percent compared with 14 percent under placebo. Caution is advised in severe kidney failure. This information does not replace medical advice.
The podcast episode (in German)
Episode 47
Magnesium L-threonate: the brain magnesium fact-checked
The podcast by Paul Höser (Episode 47) · with Paul & Paula. The MIT discovery, the only magnesium form shown to reach the brain: Slutsky (Neuron 2010), Liu (J Alzheimers Dis 2016: cognitive age ~9 years younger), sleep study 2024 (more deep and REM sleep). Plus a two-track strategy with base magnesium and a buying checklist. Information only, no dosage or usage recommendation.
Related
- Works together withVitamin D3
- Works together withZinc
- Same categoryElectrolytes
- Same categoryIron
- Same categoryIodine
- Also for energy and nervesVitamin B complex
Sources
- Garrison 2020, Cochrane Database of Systematic Reviews CD009402.pub3 – 11 RCTs, calf cramps (PMID 32956536)
- Kuusipalo 2026, Trials – three-arm multicenter RCT, magnesium and compression stockings (PMID 41680812)
- Schuster 2025, Nature and Science of Sleep – double-blind RCT, 155 participants, sleep (PMID 40918053)
- Lopresti 2026 – review of 12 RCTs on magnesium and sleep (PMID 42661485)
- BfR – Proposed maximum levels for magnesium in foods including food supplements
Open in the database – with search, filters and comparison (German app)
Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-09-13.