Magnesium L-threonate (branded Magtein) is magnesium bound to L-threonic acid, a vitamin-C metabolite. It was developed specifically on the hypothesis that it raises magnesium levels in the brain better than other forms, and is sold as a cognition/“brain magnesium” supplement. The mechanism is interesting and the rodent work is real — but the human evidence is thin and mostly industry-linked, so the marketing runs well ahead of the data. For magnesium’s established uses, see Magnesium.
What the Evidence Says
Only two small human RCTs exist. The first (MMFS-01, n=44) reported cognitive improvement in older adults with subjective cognitive decline, but it was a single-site trial funded by the compound’s commercial developer, and the tested formula also contained vitamins C and D 1Reference 1RCTEfficacy and safety of MMFS-01 (magnesium L-threonate) for cognitive impairment in older adults — randomised, double-blind, placebo-controlled trial (small, industry-funded)View study →. A 2026 branded trial (n=100) reported a reduced “brain age” measure but found no difference on a core fluid-intelligence test versus placebo 2Reference 2RCTEffects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality in adults — randomised, double-blind, placebo-controlled trial (branded; null on fluid-intelligence test)View study →. Most of the supporting data are rodent studies, and there is no independent replication.
Gap: the cognition claim rests on two small, industry-linked human trials with mixed endpoints and no independent confirmation — treat “magnesium for the brain” as a hypothesis, not an established benefit.
Absorption & Tolerability
L-threonate is low in elemental magnesium (~8% by weight), so the studied dose (~1.5–2 g of compound) delivers only ~144 mg of elemental magnesium — less than a typical magnesium supplement — which also makes it an expensive way to raise whole-body magnesium. It is well tolerated in the short trials to date.
Dosage
The trials used about 1,500–2,000 mg of the compound per day (roughly 144 mg elemental magnesium), usually split. Commonly studied range, not a personal recommendation; see Magnesium for intake references.
Safety
Well tolerated in short studies. General magnesium cautions apply — avoid unsupervised use in kidney impairment, and mind drug-timing interactions (see Magnesium). Long-term safety at these doses is not well characterised.
References
- Liu G, Weinger JG, Lu ZL, Xue F, Sadeghpour S. (2016). Efficacy and safety of MMFS-01 (magnesium L-threonate) for cognitive impairment in older adults — randomised, double-blind, placebo-controlled trial (small, industry-funded). Journal of Alzheimer’s Disease, 49(4), 971–990. https://pubmed.ncbi.nlm.nih.gov/26519439/
- Lopresti AL, Smith SJ. (2026). Effects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality in adults — randomised, double-blind, placebo-controlled trial (branded; null on fluid-intelligence test). Frontiers in Nutrition, 12, 1729164. https://pubmed.ncbi.nlm.nih.gov/41601871/