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Sunday, May 22, 2011

What is Homocysteine ?

[This a very informative article extracted from the web page of http://www.medicinenet.com]

Homocysteine is an amino acid that is produced by the body, usually as a byproduct of consuming meat. Amino acids are naturally made products, which are the building blocks of all the proteins in the body.

Elevated levels of homocysteine (>10 micromoles/liter) in the blood, may be associated with atherosclerosis (hardening and narrowing of the arteries) as well as an increased risk of heart attacks, strokes, blood clot formation, and possibly Alzheimer's disease.

Theoretically, an elevated level of homocysteine in the blood (hyperhomocysteinemia) is believed to cause narrowing and hardening of the arteries (atherosclerosis). This narrowing and hardening of the vessels is thought to occur through a variety of ways involving elevated homocysteine. The blood vessel narrowing in turn leads to diminished blood flow through the affected arteries.

Elevated levels of homocysteine in the blood may also increase the tendency to excessive blood clotting. Blood clots inside the arteries can further diminish the flow of blood. The resultant lack of blood supply to the heart muscles may cause heart attacks, and the lack of blood supply to the brain causes strokes.

Elevated homocysteine levels also have been shown to be associated with formation of blood clots in veins (deep vein thrombosis and pulmonary embolism). The mechanism is complex, but it is similar to the way that they contribute to atherosclerosis. In some studies, even moderate levels of homocysteine level showed higher rates of repeated incidence of blood clot formation.

Homocysteine levels are measured in the blood by taking a blood sample. Normal levels are in the range between 5 to 15 micromoles (measurement unit of small amount of a molecule) per liter. Elevated levels are classified as follows :
  • 15-30 micromoles per liter as moderate
  • 30-100 micromoles per liter as intermediate
  • Greater than 100 micromoles per liter as severe
Homocysteine is chemically transformed into methionine and cysteine (similar amino acids) with the help of folic acid, vitamin B12, and vitamin B6. This transformation utilizes a set of mediator molecules (called enzymes) and happens via a delicate sequence of specific steps.

Therefore, insufficient amounts of these vitamins in the body can hamper the natural breakdown of homocysteine. In addition, if there are any deficiencies in the mediator molecules, the breakdown is also hampered. This can cause homocysteine to accumulate in the blood because its breakdown is slow and inadequate.

Can nutritional problems cause elevated homocysteine levels ?

The other more common (5%-7% of the population) and less severe type of elevated homocysteine level may be caused by nutritional deficiencies in folate, vitamin B6 and vitamin B12, chronic (long-term) kidney disease, and cigarette smoking.

As mentioned above, these vitamins are essential in the breakdown of homocysteine. In some studies, lower levels of these vitamins, especially folate, have been demonstrated in people with elevated homocysteine levels. On the other hand, other studies have suggested that adequate intake of folate, Vitamin B6, and Vitamin B12 have resulted in lowering of the homocysteine level.
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How can homocysteine levels be lowered ?
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The consumption of folic acid supplements or cereals that are fortified with folic acid, and to a lesser extent vitamins B6 and B12, can lower blood homocysteine levels. These supplements may even be beneficial in people with mild genetic hyperhomocysteinemia to lower their homocysteine levels. However, it is noteworthy that so far there is no compelling data to support the treatment of hyperhomocysteinemia for prevention of heart disease or treatment of known heart disease or blood clots. There are many studies underway to determine whether there may be any benefit to treat high levels of homocysteine in patients with known heart disease or blood clots. Further recommendations may be available when these studies are completed.
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Does lowering homocysteine levels prevent heart attacks and
strokes ?
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Currently, there is no direct proof that taking folic acid and B vitamins to lower homocysteine levels prevents heart attacks and strokes. However, in a large population study involving women, those who had the highest consumption of folic acid (usually in the form of multivitamins) had fewer heart attacks than those who consumed the least amount of folic acid. In this study, the association between dietary intake of folate and vitamin B6 and risk of heart disease was more noticeable than between dietary intake of vitamin B12 and heart disease, which was minimal.
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What should I do to prevent heart attacks and strokes ?
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Losing excess weight, exercising regularly, controlling diabetes and high blood pressure, lowering the bad LDL cholesterol, and stopping cigarette smoking are crucial steps in preventing heart attacks and strokes. The association between homocysteine levels and atherosclerosis is generally weaker compared to the known risk factors of diabetes, high blood pressure (hypertension), high cholesterol level, and cigarette smoking.
It is recommended that healthy adults eat more fresh fruits and vegetable, eat less saturated fat and cholesterol.

To summarize
Homocysteine is an amino acid (a building block of protein) that is produced in the human body.

High homocysteine levels in the blood can damage the lining of the arteries. In addition, high homocysteine levels may make blood clot more easily than it should. This can increase the risk of blood vessel blockages. A clot inside your blood vessel is called a thrombus. A thrombus can travel in the bloodstream and get stuck in your lungs (called a pulmonary embolism), in your brain (which can cause a stroke) or in your heart (which can cause a heart attack.) People who have very high levels of homocysteine are at an increased risk for coronary artery disease.

Homocysteine is normally changed into other amino acids for use by the body. If your homocysteine level is too high, you may not be getting enough B vitamins to help your body use the homocysteine.

Most people who have a high homocysteine level don't get enough folate (also called folic acid), vitamin B6 or vitamin B12 in their diet. Replacing these vitamins often helps return the homocysteine level to normal. Other possible causes of a high homocysteine level include low levels of thyroid hormone, kidney disease, psoriasis, some medicines or when the condition runs in your family.

Homocysteine is measured using a simple blood test. You don't have to prepare in any special way for the blood test.

If your homocysteine level is too high, you need to lower it, especially if you have blockages in your blood vessels. If you have no other major risk factors for cardiovascular disease and you do not have atherosclerosis (a buildup of plaque in your arteries), your doctor may take a watchful waiting approach and monitor the level closely. If your homosysteine level increases further, you may need to lower it.

While no studies have shown that lowering homocysteine levels helps reduce strokes, heart attacks and other cardiovascular conditions, it is a good idea to lower a high homocysteine level because it is a risk for heart disease.

Eating more fruits and vegetables (especially leafy green vegetables) can help lower your homocysteine level by increasing how much folate you get in your diet. Good sources of folate include many breakfast cereals, fortified grain products, lentils, asparagus, spinach and most beans.

If you don't have enough vitamin B-6 in your diet, foods such as fortified breakfast cereals, potatoes, bananas, garbanzo beans (also called chickpeas) and chicken are good sources. Dairy products, organ meats (such as liver), beef and some types of fish are good sources of vitamin B-12 .

If adjusting your diet is not enough to lower your homocysteine, your doctor may suggest that you take a folate supplement. You may also need to take a vitamin B-6 and vitamin B-12 supplement.Eating more fruits and vegetables (especially leafy green vegetables) can help lower your homocysteine level by increasing how much folate you get in your diet. Good sources of folate include many breakfast cereals, fortified grain products, lentils, asparagus, spinach and most beans.

If you don't have enough vitamin B-6 in your diet, foods such as fortified breakfast cereals, potatoes, bananas, garbanzo beans (also called chickpeas) and chicken are good sources. Dairy products, organ meats (such as liver), beef and some types of fish are good sources of vitamin B-12 .

If adjusting your diet is not enough to lower your homocysteine, your doctor may suggest that you take a folate supplement. You may also need to take a vitamin B-6 and vitamin B-12 supplement.

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