Neurological · MAG-NEU-01 · v2
Most of the small trials here point the same way: people taking magnesium tended to have fewer migraine attacks. Several studies report a clear reduction, and one crossover trial found magnesium roughly as good as a standard preventive drug, valproate [3]. But the single best-designed study that compared a magnesium-containing supplement against a dummy pill did not show a real difference in migraine days [2], and a head-to-head trial found magnesium on its own worked less well than the drug it was tested against [1]. Many of the positive trials had no dummy-pill comparison, were done almost entirely in one country, and used small numbers of patients. So while the overall picture leans favourable, the strongest evidence is weak and mixed, which is why the panel did not treat the claim as settled.
Placebo-controlled and multi-arm trials report magnesium-attributable reductions in attack frequency: [5] found magnesium superior to placebo (p<0.001), [4] reported a significant reduction in migraine frequency across groups (p=0.008) with a nested model attributing an effect to magnesium, and [7] found a significant difference in attack number at three months (P=0.004). A crossover trial [3] found magnesium oxide comparable to valproate in prophylaxis. Against this, the most rigorous placebo-controlled frequency test [2] showed migraine days falling from 6.2 to 4.4 versus 6.2 to 5.2 on placebo, a non-significant difference (p=0.23), and in the direct head-to-head [1] magnesium alone underperformed the valproate and combination arms (P<0.001). The corpus therefore shows a direction-consistent but methodologically weak signal. The contested point: The division is between the several positive frequency results ([4],[5],[7]) and the fact that the single most rigorous placebo-controlled frequency endpoint missed significance [2] while the one clean head-to-head [1] showed magnesium monotherapy underperforming. Whether the positive signal reflects a real magnesium effect or the weak designs (no placebo arm, fixed combinations, confounded controls) is exactly what the corpus cannot resolve.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
The only rigorous placebo-controlled test of a magnesium-containing supplement on frequency [2] was non-significant (migraine days p=0.23 vs placebo); the headline supportive trials are either not placebo-controlled or low quality.
Indirectness: [2] and [8] deliver magnesium in fixed combinations (riboflavin/Q10; B12+exercise), so no frequency reduction can be attributed to magnesium itself.
Where it remains uncertain. The most rigorous placebo-controlled frequency endpoint was non-significant (p=0.23) [2], and a direct head-to-head showed magnesium alone underperforming its comparators (P<0.001) [1].
Aleatory
Trials are small (e.g. [5] N=87, [3] N=63, [7] N=100), so results are vulnerable to chance variation in attack counts.
Epistemic
[2] delivers magnesium with riboflavin and Q10, and [8] with B12 and exercise, so any frequency change cannot be isolated to magnesium.
Inferential
[7] compares migraine patients on magnesium against healthy controls on placebo, weakening any inference about frequency reduction.
The load-bearing papers from a corpus of 12, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Counter-evidence: magnesium-alone arm significantly underperformed valproate and combination arms.
“group C could not effectively reduce measured parameters in the patients, compared to groups A and B after 3 months (P < 0.001).”
Panel auditInternal validity: medium · scope of inference: Adults 18-65 with ≥4 monthly attacks, magnesium as monotherapy vs valproate-containing regimens over 3 months.Key limitations: no placebo arm · magnesium alone inferior to comparators · single-center
Best-designed placebo-controlled trial: frequency (migraine-day) endpoint not significant; magnesium in combination.
“Migraine days per month declined from 6.2 days during the baseline period to 4.4 days at the end of the treatment with the supplement and from 6.2.days to 5.2 days in the placebo group (p = 0.23 compared to placebo).”
Panel auditInternal validity: high · scope of inference: Adults 18-65 with ≥3 attacks/month; effect of a magnesium-containing combination on migraine days over 3 months.Key limitations: combination product confounds magnesium effect · frequency endpoint non-significant
Crossover RCT: magnesium comparable to an established prophylactic (active comparator, no placebo).
“This study has shown that 500 mg magnesium oxide appears to be effective in migraine prophylaxis similar to valproate sodium without significant adverse effect.”
Panel auditInternal validity: medium · scope of inference: Migraine patients receiving magnesium oxide vs valproate over 8-week periods; comparative, not placebo-referenced.Key limitations: no placebo arm · equivalence to active drug does not prove reduction · 7 dropouts
Frequency reduction is attributed to the HIIT+Supp combination versus other groups, and the supplement bundles B12, so the magnesium-specific effect on frequency cannot be isolated.
Panel auditInternal validity: low · scope of inference: Women with migraine over 2 months; combined exercise plus B12+magnesium on migraine measures.Key limitations: magnesium confounded with B12 and exercise · effect credited to combination · small sample, women only
4 of 12 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.
The corpus points toward a frequency benefit but the strongest-designed trial missed the endpoint and key positives are confounded or low quality, so the claim sits in the Uncertain band.
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.
No placebo-controlled magnesium-monotherapy frequency trial. Every rigorous placebo comparison here uses a fixed combination [2] or has no placebo arm [1],[3], so a magnesium-specific frequency effect is never cleanly isolated. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A large, double-blind, placebo-controlled RCT of magnesium alone with monthly migraine days as the pre-registered primary endpoint.
Open question: Does magnesium monotherapy reduce migraine frequency versus placebo when tested as the primary endpoint? Why it is still open: The only rigorous placebo-controlled frequency test [2] used a fixed combination and was non-significant (p=0.23); no clean monotherapy-versus-placebo frequency trial exists in the corpus.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 18 Sep 2026 · protocol v0.19