Axons are usually surrounded by a fatty substance called myelin. Myelin allows action potentials to propagate quickly from one neuron to another, allowing for rapid signal transmission. It is a critical part of the nervous system and it's absence has devastating effects, as seen in conditions such as multiple sclerosis.
Researchers have found that patients with low levels of folate in their blood are more likely to develop hearing loss (Gok 2004; Lasisi 2010; Gopinath 2010), and that low vitamin B12 levels are associated with hearing loss (Gok 2004) and tinnitus (Shemesh 1993).
Food rich in Vitamin B12 or cobalamine help improve hearing by regulating the formation of red blood cells, assisting in the metabolism of homocysteine, and preventing tinnitus. Sources of Vitamin B12: dairy products, eggs, lean beef, shellfish. Food rich in Folic Acid lowers the production of homocysteine which is thought to be the cause of some kinds of hearing loss and boosts circulation of blood to the inner structures of the ear.