What is Homocystein?
Homocystein (say: "ho-mo-sist-een")
is an amino acid (a building block of protein) that is produced in the human
body.
Epidemiological studies have shown that
too much Homocystein in the blood (plasma) is related to a higher risk of
coronary heart disease, stroke and peripheral vascular disease.
Homocystein may irritate
blood vessels
and damage the inner lining of arteries and
promote blood clots,
leading to blockages in the arteries (called
atherosclerosis).
Why is a high Homocystein level harmful?
High Homocystein levels in
the blood can cause cholesterol to change to something called oxidized
low-density lipoprotein, which is more damaging to the arteries. In addition,
high Homocystein levels can make blood clot more easily than it should,
increasing the risk of blood vessel blockages. A blockage might cause you to
have a stroke or a problem with blood flow. Up to 20% of people with heart
disease have high Homocystein levels.
What causes a high Homocystein level?
Plasma Homocystein levels are strongly
influenced by diet, as well as by genetic factors. The dietary components with
the greatest effects are folic acid and vitamins B6 and B12. Folic acid and
other B vitamins help break down Homocystein in the body. Several studies have
found that higher blood levels of B vitamins are related, at least partly, to
lower concentrations of Homocystein. Other recent evidence shows that low blood
levels of folic acid are linked with a higher risk of fatal coronary heart
disease and stroke.
Homocystein is normally
changed into other amino acids for use by the body. If your Homocystein level is
too high, you may not have enough B vitamins to help this process. Or you may
not have enough of the chemicals (enzymes) to process Homocystein.
Most people with a high
Homocystein level don't get enough folate (also called folic acid), vitamin B6
or vitamin B12
in their diet. Replacing these vitamins helps return the Homocystein level to
normal. Other possible causes of a high Homocystein level include low levels of
thyroid hormone, kidney disease, psoriasis, some medicines, or inherited
deficiencies in the enzymes used to process Homocystein in the body.
Recent findings suggest that laboratory
testing for plasma Homocystein levels can improve the assessment of risk. It may
be particularly useful in patients with a personal or family history of
cardiovascular disease, but in whom the well-established risk factors (smoking,
high blood cholesterol, high blood pressure) do not exist.
How is the Homocystein level measured,
and what do the results mean?
Homocystein is measured
using a simple blood test. It can be measured at any time of day. It is not
necessary to prepare in any special way for the blood test (such as fasting).
Most hospital labs can measure Homocystein, or a blood sample can be sent out to
a special lab.
A healthy Homocystein
level is less than 12 µmol per L. A level greater than 12 µmol per L is
considered high. If your Homocystein level is 12 to 15 µmol per L and you have
blockages in any blood vessel, you need to lower your Homocystein to less than
12 µmol per L. If you have no other major risk factors for cardiovascular
disease and you do not have atherosclerosis, it may be okay for you to have a
modestly high level of Homocystein (12 to 15 µmol per L).
While no studies have
proved that lowering Homocystein levels ultimately helps reduce strokes, heart
attacks and other cardiovascular events, it is a good idea to lower a high
Homocystein level because it is a risk for heart disease.
How can I lower a high Homocystein
level?
Eating more fruits and
vegetables (especially leafy green vegetables) can help lower your Homocystein
level by increasing how much folate you get in your diet. Good sources of folate
include many breakfast cereals, lentils, chickpeas, asparagus, spinach and most
beans. Folate is sometimes called "folic acid."
If adjusting your diet is
not enough to lower your Homocystein, you will also need to take specific
vitamins. You may need to take a fairly large amount of folate (about 1
milligram per day). Additional vitamin B6
and vitamin B12 also help the body process Homocystein. Vitamin B
supplements generally have no side effects.
The usual recommended
vitamin and folate doses for lowering Homocystein levels are as follows:
- A daily
multivitamin containing 400 µg of folate and less than 5 mEq of iron
- An additional 800
µg of folate per day for 8 weeks
If taking these vitamins
doesn't lower your Homocystein level, your doctor may have you try a higher
dose. Or you may need to have some tests to see if you have a health condition
that causes high Homocystein levels.
What happens next?
It is important to get
your Homocystein level rechecked after you have been taking the multivitamin and
folate for 8 weeks. If your Homocystein level remains high, your doctor may
change your treatment. You may need to take more folate (2 mg per day). If you
have had a high Homocystein level, you will probably need to have your level
checked regularly - maybe 2 or 3 times a year.
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