Supplement evidence
Magnesium
What the trials measured, and what deficiency correction does and does not tell you.
What Its Legal Status Actually Means
Read this before anything below it. Legal to sell is not the same fact as reviewed, verified, or approved.
Oral magnesium sold for mood, anxiety, or sleep is a dietary supplement under the Dietary Supplement Health and Education Act of 1994 (DSHEA). The FDA does not review it for safety or effectiveness before sale, does not verify label content, and has never approved any magnesium supplement to prevent or treat depression, anxiety, or insomnia. Magnesium does have a recognised Recommended Dietary Allowance (roughly 310-420 mg/day of elemental magnesium for adults, set by the National Academies) and a Tolerable Upper Intake Level of 350 mg/day from supplements specifically, and separate FDA-approved prescription and OTC magnesium products exist for entirely different purposes — magnesium sulfate injection for eclampsia, magnesium hydroxide and citrate as laxatives and antacids. None of those approvals apply to mental health. Different salts (oxide, citrate, glycinate, threonate) differ substantially in elemental magnesium content and absorption, so doses are not interchangeable between bottles.
Quoted whole from the 2026-08-18 study harvest. Not summarized, not shortened.
What the Research Shows
5 records from the 2026-08-18 harvest, each checked against PubMed and Europe PMC on that date. How a study was designed, how many people were in it, and who paid for it are printed above what it found, because those three facts decide how much the finding is worth.
Study 1 · 2025
- Systematic review of observational studies
- 63,214 participants
- Reputable journal
- Independently funded
- Preregistered
strong82/100Well-supported by good-quality research.
Read this first: Entirely observational. Mostly cross-sectional studies, which cannot establish that low magnesium came before the depression rather than after it, and dietary magnesium intake is a proxy for overall diet quality, socioeconomic position, and physical activity. No supplement was tested in any of the pooled studies.
Pooling 10 cross-sectional and 3 cohort studies covering 63,214 adults, people in the highest category of dietary magnesium intake had a 34% lower risk of depression than those in the lowest (relative risk 0.66, 95% CI 0.57-0.78), and each additional 100 mg/day of dietary magnesium was associated with 7% lower risk (RR 0.93, 95% CI 0.90-0.96). This is an association between what people eat and how they feel, not evidence that a magnesium pill treats depression — depression itself changes appetite and diet quality, and magnesium-rich diets are also rich in everything else that comes with vegetables, nuts, and whole grains.
How this record was checked
PubMed record 38812090 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, the 63,214 participants across 10 cross-sectional and 3 cohort studies, RR 0.66 (95% CI 0.57-0.78), the per-100 mg RR 0.93 (95% CI 0.90-0.96), and PROSPERO registration CRD42024506570 confirmed verbatim from the abstract. Europe PMC core record fetched 2026-08-18 lists funding from "Isfahan University of Medical Sciences" (grant 140274) and its Student Research Committee, with no commercial sponsor, hence funding INDEPENDENT.
Study 2 · 2017
- Randomized trial
- 126 participants
- Indexed journal
- Independently funded
- Declared conflicts of interest
strong76/100Well-supported by good-quality research.
Read this first: Open-label with a no-treatment control rather than a placebo. That single design choice makes the headline 6-point PHQ-9 improvement uninterpretable as a drug effect: placebo responses of that magnitude are routine in depression trials, and here nothing separated the magnesium effect from the effect of knowingly starting a treatment. The authors' conclusion that "magnesium is effective for mild-to-moderate depression" outruns what an unblinded design can show.
One hundred twenty-six primary-care adults with mild-to-moderate depression (PHQ-9 scores 5-19) took 248 mg of elemental magnesium daily for six weeks and no treatment for six weeks, in randomized order. PHQ-9 scores improved by a net 6.0 points (95% CI 4.2-7.9) and anxiety scores on the GAD-7 by 4.5 points during the magnesium periods, with effects appearing within two weeks and good tolerability. The crucial caveat is in the design: the control condition was no treatment at all, and neither participants nor investigators were blinded, so a large share of that 6-point improvement is the expectation of being treated.
How this record was checked
PubMed record 28654669 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, N=126 randomized (112 providing analyzable data), the 248 mg elemental magnesium dose, the six-week crossover periods, and the PHQ-9 (-6.0, CI -7.9 to -4.2) and GAD-7 (-4.5, CI -6.6 to -2.4) results confirmed verbatim from the abstract; the record's competing-interests statement reads "The authors have declared that no competing interests exist." Europe PMC core record fetched 2026-08-18 lists the funder as "the Henry and Carleen Tufo fund of the University of Vermont", hence funding INDEPENDENT.
Study 3 · 2023
- Meta-analysis of randomized trials
- Reputable journal
- Funding not established
- Preregistered
moderate69/100Reasonable evidence with real limitations.
Read this first: The mineral analysis pooled iron, zinc, and magnesium together rather than testing magnesium alone, and the population was perinatal, so this is a null result in a specific setting rather than a definitive negative for magnesium in depression generally. The wide confidence interval reflects few trials.
Across 36 randomized trials of dietary interventions for depression and anxiety in pregnancy and after birth, 28 of them pooled, elemental minerals including magnesium were not superior to placebo for perinatal depression (standardized mean difference -0.42, 95% CI -1.05 to 0.21 — a confidence interval that crosses zero). Omega-3 fatty acids also failed; only vitamin D produced a small-to-medium benefit in postpartum depression.
How this record was checked
PubMed record 37019362 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, the 36 included and 28 pooled studies, the elemental-metals estimate (SMD -0.42, 95% CI -1.05 to 0.21), the vitamin D result, and PROSPERO registration CRD42020208830 confirmed verbatim from the abstract. Europe PMC core record fetched 2026-08-18 returned no grant or funding list and the publisher page was not retrievable, so funding is recorded UNKNOWN rather than inferred.
Study 4 · 2018
- Randomized trial
- 37 participants
- Indexed journal
- Independently funded
- Declared conflicts of interest
strong74/100Well-supported by good-quality research.
Read this first: The authors' own stated limitation is the small sample: 37 people cannot rule out a modest real benefit, so this is an absence of evidence rather than firm evidence of absence. The 120 mg/day dose is also low relative to the 248 mg used in the Tarleton trial, which the authors themselves flag as a possible explanation.
Thirty-seven patients with recurrent depressive disorder in a depressive episode were randomized, double-blind, to fluoxetine plus 120 mg/day of magnesium ions or fluoxetine plus placebo for eight weeks. There was no significant difference between the groups on the Hamilton Depression Rating Scale at any point, and no difference in serum magnesium either. A secondary multivariate model suggested magnesium augmentation was among several factors associated with better odds of response, but that is an exploratory analysis in 37 people and does not overturn the trial's negative primary result.
How this record was checked
PubMed record 30081500 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, N=37, the 120 mg/day magnesium aspartate dose, the eight-week double-blind design, and the finding of "no significant differences in either Hamilton Depression Rating Scale (HDRS) scores or serum magnesium levels at any stage of treatment" confirmed verbatim from the abstract; the record's conflict statement reads "All authors declare no conflict of interest." Europe PMC core record fetched 2026-08-18 lists Polish National Science Centre grant NCN2012/07/B/NZ7/04375 and statutory funding from the Medical University of Warsaw and the Institute of Pharmacology PAS, hence funding INDEPENDENT.
Study 5 · 2017
- Systematic review of randomized trials
- Indexed journal
- Industry funded
- Declared conflicts of interest
early signal49/100Suggestive but preliminary. Not settled.
Read this first: The acknowledgments state that two of the three authors "received funding from Sanofi to conduct the initial systematic publication database search" and that "Sanofi also provided access to data from 3 unpublished Mg intervention studies"; the senior author separately discloses membership of the Sanofi Consumer Healthcare Advisory Board. Sanofi markets magnesium supplements, so the sponsor had a direct commercial interest in the review's conclusion, and unpublished sponsor-held data entered the evidence base without independent scrutiny. Many included studies tested magnesium combined with up to five other ingredients.
The most-cited review of magnesium for anxiety included 18 studies, all in groups already vulnerable to anxiety (mildly anxious, premenstrual syndrome, postpartum, hypertensive). The tally was mixed rather than convincing: 4 of 8 studies in anxious samples, 4 of 7 in PMS samples, and 1 of 2 in hypertensive samples reported a benefit, magnesium had no effect on postpartum anxiety, and not one study used a validated measure of subjective stress. The authors' own conclusion is that the evidence is "suggestive" but that "the quality of the existing evidence is poor."
How this record was checked
PubMed record 28445426 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, the 18 included studies, the 4/8, 4/7 and 1/2 positive-study tallies, the null postpartum result, and the "quality of the existing evidence is poor" conclusion confirmed verbatim from the abstract, along with the conflict statement naming L.D.'s Sanofi Consumer Healthcare Advisory Board membership. Europe PMC full text (PMC5452159) retrieved 2026-08-18: the Acknowledgments read "The authors N.B. and C.L. received funding from Sanofi to conduct the initial systematic publication database search of the effects of Mg on subjective stress and anxiety. Sanofi also provided access to data from 3 unpublished Mg intervention studies", hence funding INDUSTRY and independent false.
The Risks
Nobody checks this purchase the way a prescription is checked. No prescriber reviews it against the rest of what you take, no pharmacist screens the interaction, and no regulator confirms the dose in the capsule before it is sold. That is why this section sits here at full length rather than as a footnote.
What the paragraph below covers:
- Heart and blood pressure
- Drug interactions
- Stomach and gut
The common and predictable adverse effect of oral magnesium is gastrointestinal: loose stools, diarrhoea, cramping and nausea, most pronounced with magnesium oxide and citrate, which is why the same salts are sold as laxatives. Anyone with reduced kidney function needs medical advice before supplementing, because the kidneys are the route by which excess magnesium is cleared, and in chronic kidney disease supplementation can produce hypermagnesaemia, causing low blood pressure, muscle weakness, confusion, irregular heartbeat, and in severe cases cardiac arrest. Magnesium binds several drugs in the gut and reduces their absorption — notably tetracycline and quinolone antibiotics, bisphosphonates, and levothyroxine — so spacing doses matters. On efficacy, the honest picture is that the strongest-looking depression trial was open-label with no placebo, the best-known anxiety review was funded by a company that sells magnesium and rated its own evidence as poor quality, a properly double-blind placebo-controlled trial of magnesium added to fluoxetine found no difference, and a meta-analysis in perinatal depression found elemental minerals no better than placebo. The reliable association between magnesium and depression comes from observational dietary studies, which cannot show that taking a supplement fixes anything.
What Is Not Known
The boundaries of the section above, in the harvest’s own words. What it excluded, why, and where it looked and found nothing. An absence of evidence is not evidence of absence, and it is not evidence of benefit either.
What Was Left Out, and Why
Quoted from the harvest, where these notes sat above the study list rather than after it. Where a note says “below” it means the studies in the section above.
- Magnesium sulfate trials in obstetrics (pre-eclampsia/eclampsia), anaesthesia, and migraine excluded: intravenous magnesium as an anticonvulsant or analgesic is a different drug in a different setting and tells a reader nothing about oral supplements for mood.
- Combination-supplement trials (magnesium plus vitamin B6, zinc, or multinutrient blends) excluded because the magnesium contribution cannot be isolated.
- Cross-sectional serum-magnesium/depression correlation studies excluded in favour of the pooled observational analysis below, which subsumes them.
The Retraction Check
PubMed efetch records for all five PMIDs inspected 2026-08-18 for "Retraction in", "Expression of concern", "Erratum in", and "Withdrawn" flags; none present.
Questions for a Prescriber or Pharmacist
This page does not tell anyone to take Magnesium or to avoid it. It is not able to: it does not know what else you take, what you have tried, or what you are treating. These are the questions each study above raises, written to be asked out loud.
- The magnesium-and-depression link comes from what people eat, not from supplements — is there any reason to think a pill would do what a better diet appears to be associated with?
- This trial compared taking magnesium against taking nothing, with everyone knowing which they were on — how much of that improvement would you expect from any pill in that setup?
- In the population where this was tested properly against placebo, magnesium and similar minerals didn't beat placebo — does that change what you'd suggest for me?
- When magnesium was tested double-blind on top of an antidepressant, it made no difference to depression scores — is adding it to my treatment worth it, or just an extra pill?
- About half the studies in the main magnesium-and-anxiety review found nothing, and the review was paid for by a supplement company — what would you want to see before I rely on it?
And the one to ask at the counter, whatever the answers above turn out to be: given everything I am already taking, what would you want to know about Magnesium before I put it in the same body?
Where This Page Comes From
Transcribed from the study-harvest-2026-08-18 record for magnesium, built into this page by scripts/supplement-ingest.mjs on 2026-09-07. Nothing here is fetched at page load, and nothing here was written by a model without a citation behind it.
| Source file | study-harvest/2026-08-18/magnesium.yaml |
|---|---|
| Source repo | REPTechnologies/avalo-backend |
| SHA-256 | 3d32fd414870ea77b1d57ba4ad6493dc2eae25203329b6b84c70bd7a4be1b854 |
| Also searched as | magnesium glycinate, magnesium citrate, magnesium oxide, magnesium chloride, magnesium aspartate, magnesium L-threonate, Magtein, Epsom salts |
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Do any supplements actually work? asks the question across all of them. The full library has the medication records, the funding investigations, and the glossary.