Studies indicates homocysteine as an independent risk factor for vascular disease (hardening of the arteries). Elevated homocysteine levels in our blood causes tremendous inflammation to our arteries.
Methionine is an essential amino aicd found mostly in meats, eggs, and dairy products. Metabolism of methionine produces homocysteine which in turn is broken down into cysteine (which is harmless) which require vitamin B6. Homocysteine can be turned back into methionine provided an enzyme in the form of vitamin B12 (as a cofactor) and folic acid (as a substrate). Therefore you need a sufficient level of vitamin B12, B6 and folic acid for homocysteine to fall within the safe range.