Magnesium L-threonate is a low-elemental magnesium salt promoted for brain delivery. The frequently cited increase in cerebrospinal-fluid magnesium comes from animals; human trials have not directly measured higher brain or CSF magnesium after oral use.
What it is, why people use it, the evidence, and what to know before trying it.
Regulatory status: supplement (oral mineral / organic salt). Not a prescription drug. Not a device, habit, or measurement. Neurocentria is developing the same ligand as a drug candidate (MMFS / L-TAMS) for ADHD, depression, and Alzheimer’s — that is a different regulatory track from the OTC Magtein bottle
Mechanism evidence: animal
Magnesium L-threonate is a real, named, low-elemental salt with a rat-CSF story and a thin, entirely industry-tied human file. What the file actually supports: two sponsor-linked RCTs (Liu 2016 n = 44 completers, composite d = 0.91 at 12 weeks; Lopresti 2026 n = 100, NIH composite +2.8 points over placebo at 6 weeks, one-tailed p = 0.043) report better *composite cognition* than placebo at ~108–145 mg elemental/day. Individual tests, Raven’s, and “N-year younger brain” arithmetic do not carry those headlines. Sleep is not established for this salt: Liu’s PSQI missed, Hausenblas’s ISI missed, Lopresti’s Oura sleep metrics missed; leftover wins are subscales and proprietary ring scores. Anxiety is a between-group null in the only RCT, published twice. ADHD and dementia remain open-label n = 15. The distinctive claim — that Magtein, unlike glycinate or oxide, raises **human** brain or CSF magnesium — has **no human measurement**. Slutsky’s +7–15% CSF is rats at 50 mg/kg/day elemental, roughly an order of magnitude above the human elemental dose. Until someone taps CSF or runs ³¹P-MRS after oral Magtein, “brain magnesium” is a marketing sentence.
Confidence: weak
Known side effects, interactions and use limits from reviewed sources.
Human safety evidence is limited and mostly short term. Magnesium supplements can cause diarrhea and may accumulate with significant kidney impairment; they can also reduce absorption of some antibiotics and other medicines when taken together.
This review does not automatically apply to:
Public protocols that include Magnesium L-threonate (Magtein) — intervention evidence review. Open one to see the full context and source.
Amount and timing patterns reported in public protocols; these are observations, not instructions. Private and hidden usage is excluded.
Brand variants reported in public protocols. Private entries are excluded, and inclusion is not an endorsement.
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