Homocysteine is a breakdown product of protein metabolism when the amino acid Methionine is converted into toxic amino acid Homocysteine. Healthy methylation processes in body will ensure that homocysteine is converted back into methionine or into another harmless compound with the aid of ‘methyl group’ nutrients: vitamins B2, B3, B6, B12 and Folic . . . → Read More: Dangers Of Homocysteine.