Musculoskeletal · MAG-MSK-02 · v2
Borderline: within 4 points of the Doubtful/Refuted boundary, so a re-grade could land either side.
The best direct test of standard magnesium for nocturnal leg cramps found it no better than a dummy pill, and the improvement people felt happened equally in both groups [7]. Two other direct trials in cramp sufferers also found no real advantage for magnesium over placebo [4], [5], and a large 2026 population study actually saw more night cramps among magnesium users [13]. The one trial that clearly favoured magnesium used a special enhanced-absorption version of the mineral rather than ordinary supplements [1]. Trials in pregnant women were split, with two positive [2], [6] and one negative [3], and they cover a different situation from ordinary night cramps. Taken together, the direct evidence points against ordinary magnesium supplements reliably reducing nocturnal leg cramps, which is why the panel placed the claim low.
The strongest population-matched trial found magnesium oxide not superior to placebo, with a difference of 0.38 cramps per week (P = .67) and the shared improvement judged a placebo effect [7]. Two further direct trials showed no significant advantage: an open-label adjunctive study (P = 0.073) [4] and a three-arm trial where magnesium versus placebo gave an adjusted mean difference of −0.20 (95% CI −1.49 to 1.09; P = 0.929) [5]. A 2026 cohort reported that magnesium users had a higher likelihood and incidence of night cramps and that supplementation did not prevent them [13]. The single positive nocturnal-cramp trial used enhanced-absorption magnesium oxide monohydrate and found a between-group reduction of −3.4 versus −2.6 episodes (p = 0.01) [1], while an intravenous trial concluded magnesium does not meaningfully reduce rest cramps in older adults [9]. The contested point: The division is whether the lone positive nocturnal-cramp result [1] reflects magnesium itself or its proprietary enhanced-absorption formulation, which no standard-formulation trial [7], [4], [5] reproduces. The pregnancy trials add a second contested strand, being internally split [2], [6] positive versus [3] negative and covering a distinct clinical entity.
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The sole positive NLC RCT [1] uses a proprietary enhanced-absorption formulation (MOMH), so it does not support the general claim about standard magnesium supplementation; the cleanest standard-formulation RCT [7] was null and attributed within-group improvement to placebo effect.
Pregnancy leg-cramp trials [2],[6],[3] address a distinct clinical entity not specified as nocturnal, and are internally contradictory (two positive, one negative) — scope drift from the NLC claim.
Where it remains uncertain. The only positive nocturnal-cramp trial used an enhanced-absorption formulation [1], and pregnancy trials are internally split [2], [6] versus [3], a distinct entity from ordinary night cramps.
Aleatory
Direct nocturnal-cramp trials are modest in size (N=94 [7], N=30 [4], N=121 [5]), leaving week-to-week cramp counts subject to chance variation.
Epistemic
The only positive nocturnal-cramp result uses enhanced-absorption MOMH [1]; whether ordinary magnesium works at a bioavailable dose is untested here.
Inferential
Pregnancy leg-cramp trials [2], [6], [3] are extrapolated to nocturnal cramps despite being a distinct entity not specified as nocturnal.
The load-bearing papers from a corpus of 13, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Only positive direct NLC RCT, but tests an enhanced-absorption formulation (MOMH).
“There was a significant between-group difference in the magnitude of reduction in NLC episodes (p = 0.01), indicating a higher decrease in the MOMH group as compared to the placebo group (- 3.4 vs - 2.6, respectively).”
Panel auditInternal validity: high · scope of inference: Adults with nocturnal leg cramps taking a specific high-absorption magnesium oxide monohydrate formulation for 60 days.Key limitations: 81% completion / attrition · single specific formulation with claimed enhanced absorption · absolute difference small (-3.4 vs -2.6)
Adjunctive magnesium in NLC shows no between-group benefit.
“there was no statistically significant difference effect between the two therapy groups based on the Mann-Whitney test (p=0.073).”
Panel auditInternal validity: low · scope of inference: NLC patients already on calcium and gabapentin; outcome is cramping pain intensity, not cramp frequency.Key limitations: open-label · very small n · adjunctive design confounds magnesium effect · pain outcome not frequency
Recent three-arm RCT: magnesium no better than placebo for leg cramp frequency.
“No significant difference was observed between the magnesium and placebo groups, with an adjusted mean difference of -0.20 (95% CI -1.49 to 1.09; P = 0.929).”
Panel auditInternal validity: high · scope of inference: Adults aged 50-85 with at least two leg cramps per week; magnesium hydrochloride daily for 4 weeks.Key limitations: partially blinded trial (stockings arm open) · magnesium a secondary comparison to primary stockings question
IV magnesium RCT/thesis conclusion negative for rest cramps in older adults.
“magnesium supplementation does not meaningfully reduce the frequency of rest cramps in older adults.”
Panel auditInternal validity: medium · scope of inference: Community-dwelling older adults with rest cramps; role in pregnancy-associated cramps left unclear.Key limitations: no effect size/p in abstract · IV route not typical consumer supplementation · pregnancy role explicitly uncertain
4 of 13 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
Predominantly null direct NLC RCT evidence outweighs a single formulation-specific positive trial, placing the claim just above Refuted.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Standard formulation head-to-head in nocturnal cramps. The single positive result depends on a proprietary enhanced-absorption formulation [1] that no standard-formulation trial reproduces [7], [4], [5]. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: Adequately powered double-blind RCT comparing a well-absorbed standard oral magnesium salt against placebo in non-pregnant adults with documented nocturnal leg cramps.
Open question: Does a standard, well-absorbed oral magnesium supplement reduce nocturnal leg cramps in non-pregnant adults? Why it is still open: The only positive nocturnal-cramp trial used enhanced-absorption MOMH [1], while standard-formulation trials were null [7], [4], [5].
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 18 Sep 2026 · protocol v0.19