Homocysteine Fact Sheet

It has been estimated that 40% of heart attacks and strokes in the US may be the result of elevated levels of homocysteine in the blood. Homocysteine is naturally produced in the body as a normal by-product of methionine (an essential amino acid) breakdown. However, it is only supposed to exist for a brief time before the body converts it into other useful substances. Problems arise when the body accumulates too much of this by-product due to a diet that does not provide the nutrients necessary to metabolize it completely and/or encourages over-production of it. High homocysteine levels prevent the normal artery wall process of repair and actually irritate the muscles of the arteries and encourage plaque formation, thus laying the foundation for cardiovascular diseases and cerebral vascular disease. A build up of homocysteine in the bloodstream is called homocysteinemia.

Jacob Selhub, Ph.D, explains that very tiny amounts of homocysteine in the blood can have an incredible impact on cardiovascular health. He gives an example that homocysteine is present in the blood at 1/1000 of the concentration of cholesterol. As little as a 20% to 30% increase in this amount of homocysteine can greatly increase the risk of cardiovascular disease. Therefore, it would behoove each individual to keep their homocysteine levels under control. Tests to assess homocysteine levels are becoming more common, ask your physician.

Homocysteine is created during the breakdown of the amino acid methionine. From there homocysteine should be broken down into cysteine or converted back into methionine. Some of the main nutrients that help the body breakdown homocysteine are several B-vitamins. An inadequate amount of B vitamins “freezes” homocysteine metabolism. Vitamin B6 converts homocysteine into harmless cystine. Therefore, adequate intake of B6 allows normal metabolism and breakdown of homocysteine. If there is inadequate amounts of this nutrient, amino acid metabolism is “stuck” at this step. Low levels of B6 allow homocysteine levels to increase and initiate the atherosclerotic process.

Folic acid and B12 are key factors in reducing homocysteine levels. Folic acid, along with B12, protect the body from high homocysteine levels by assisting another enzyme in converting homocysteine back to the amino acid methionine. If the body does not have adequate amounts of folic acid, homocysteine begins to accumulate. Vitamin B12 deficiencies are more common in people during mid- to late life and in strict vegetarians. As many as 15% of the elderly may have B12 deficiencies. Therefore, it is important to make sure that one gets adequate amounts of this nutrient as well.

Folic acid, vitamin B6, and vitamin B12 interrupt the production of homocysteine or help quench its metabolism. Each nutrient functions at a different stage, however, they all lower the blood levels of homocysteine and reduce the risk of cardiovascular disease. Unfortunately, nutritional surveys confirm that deficiencies of the B vitamins are prevalent in Americans. These widespread B vitamin deficiencies result in dangerously high homocysteine levels.

It is recommended to increase foods that contain high amounts of B complex vitamins, particularly folic acid, B6. and B12. Folic acid and B6 can be obtained through foods such as brewer’s yeast, soybeans, nuts and seeds, and dark leafy greens. The best sources of B12 come from animal sources, including dairy, eggs, meat and poultry, and fish. Overall, supplementing with a full spectrum B complex vitamin is a good idea to ensure adequate intake of these vital nutrients for maintaining healthy homocysteine levels.


Challem, Jack. 1996. Homocysteine: The new “Cholesterol.” Keats Good Health Guide.

Murray, Michael, N.D. 1996. Encyclopedia of Nutritional Supplements. Prima Publishing.