Homocysteine Molecular Structure
Homocysteine is an amino acid that naturally occurs on humans. It is not ingested in the diet in significant quantities but rather is biosynthesized in a complex series of steps from methionine. High levels of homocysteine have been linked to various types of cardiovascular disease, including heart attack and stroke. Unfortunately there is no conclusive evidence that measures to attempt to primarily lower homocysteine levels can reduce cardiovascular risks.
Homocysteine levels are influenced by several of the B vitamins, especially vitamins B12, folic acid and B6 (pyridoxine). Vitamin B12 deficiency especially has been linked to high levels of homocysteine. Despite the correlation between high levels of homocysteine and cardiovascular disease a recent Cochrane review showed that in a review of 8 major studies there was no evidence that homocysteine lowering interventions reduced human’s risk of cardiovascular events.
Homocysteine is not one of the 20 amino acids used in the body for protein synthesis. Rather it is an amino acid that occurs as one step of the production of methionine, a non-essential amino acid. Amino acids are considered essential if they must be ingested in the diet and cannot be synthesized by humans from other building blocks. Because methionine is a non-essential amino acid it can be synthesized, and homocysteine is one of the precursor amino acids in this step-wise synthesis.
Eating a diet rich in fruits and vegetables is probably the number one thing we can do to try to lower our homocysteine levels. Fruits and vegetables are the dietary way we ingest folic acid, one of the vitamins most critical to keeping homocysteine levels down. B12 is another critical vitamin in this metabolic pathway, and B12 is found in many foods in the diet, but essentially only in animal products. Vegans can easily become B12 deficient if they do not take supplemental sources of vitamin B12. Pyridoxine, vitamin B6, is found in many fruits and foods like bananas, potatoes, and chicken. It is also added as a food supplement as part of the U.S. food vitamin fortification program and deficiency in pyridoxine is uncommon.
Homocysteine, especially high levels of homocysteine, can be a powerful risk factor for cardiovascular disease and a good diet with or without vitamin supplementation is the key to avoiding the risks of a high level. High levels of homocysteine can run in some families, and this may be one of the mechanisms by which cardiovascular disease is hereditary.