Methylcobalamin (Methyl B-12) is better absorbed and retained than other forms of B12 (such as cyanocobalamin). Methyl B12 protects nerve tissue and brain cells, and promotes better sleep. Methyl B12 is an important cofactor that is needed to reduce toxic homocysteine to the essential amino acids methionine. Methylcobalamin also protects eye function against toxicity caused by excess glutamate. Also, vegetarians/vegans typically require B12 supplementation.