NOW Supplements Magnesium (Mg) is an essential mineral best known for its role in bone and nervous system function.* Recent research has demonstrated that it is also critical for normal brain health and normal cognitive function by maintaining the density and stability of neuronal synapses.* However, most forms of Mg are not easily absorbed into the nervous system.* Magtein® is a patented form of Mg that readily crosses the blood-brain barrier for utilization in the brain.* Laboratory studies indicate that Magtein® supports brain health and may facilitate learning and memory, as well as a relaxed mood.*