Magnesium L-Threonate (Magtein) is a brain-targeted mineral compound with the most robust central nervous system permeability of any magnesium form, primarily acting through blood-brain barrier penetration and synaptic density support. Best for: individuals seeking long-term cognitive longevity, professionals optimizing stress resilience, and those addressing daytime fatigue or autonomic recovery (HRV). Not worth it if: you want an acute, stimulant-style productivity boost. E