Which mineral assists in transporting sodium to the brain and muscles?

Lithium is the mineral that plays a crucial role in neurotransmission, specifically in the transport of sodium in the brain. It is known to influence sodium transport and can enhance the function of sodium channels, which are essential for maintaining the resting membrane potential and for the generation and propagation of action potentials in neurons. This function is particularly relevant for brain activity and overall neurological health.

While the other minerals listed, such as vanadium, zinc, and iron, have their own important roles in the body—like iron being vital for oxygen transport and zinc being essential for immune function and enzyme activity—they do not specifically facilitate the transport of sodium to the brain and muscles in the way that lithium does. Hence, lithium's unique role in neuronal function and sodium transport makes it the correct answer to the question.