Vitamin B12, may help to prevent Parkinson's disease and slow the progression in those who already have the disease by protecting against the neural toxicity caused by excess L-dopamine, a probable cause of the disease.  

The vitamin has been shown to reverse the symptoms of rare neurological disease's such as Bell's palsy and shows promise in the treatment of multiple sclerosis and other neurological diseases. 

Vitamin B12 is needed to prevent anemia; it aids folic acid in regulating the formation of red blood cells, and helps in the utilization of iron. This vitamin is also required for proper digestion   of foods and the metabolism of carbohydrates and fats. It aids in cell formation and cellular longevity. In addition, vitamin B12 prevents nerve damage, maintains fertility, and promotes normal growth and development by maintaining the fatty sheaths that cover and protect nerve endings.  

Vitamin B12  supplementation has been shown to enhance sleep patterns, allowing for more restful and refreshing sleep.  

 A vitamin B12  deficiency can be caused by mal-absorption, which is most common in older adults and in people with digestive disorders. Deficiency can cause abnormal gait, bone loss, chronic fatigue, constipation, depression, digestive disorders, dizziness, drowsiness, enlargement of the liver, eye disorders, hallucinations, headaches (including migraines), inflammation of the tongue, irritability, labored breathing, memory loss, moodiness, nervousness, neurological damage, palpitations, pernicious anemia, ringing in the ears, and spinal cord degeneration.  

Researchers caution that all patients with unexplained anemia  and/or neurological symptoms, as well as patients at risk for developing low B12 levels like the elderly and those with intestinal disorders, should have blood levels measured.  In addition, those with cognitive  impairment may want to be tested for low B12 levels.