HOMOCYSTEINE, FOLIC ACID AND CARDIOVASCULAR DISEASE
AHA Recommendation
The American Heart Association does not recommend widespread use of folic acid and B
vitamins to reduce the risk of heart disease and stroke (brain attack). The AHA advises
a healthy, balanced diet that includes five servings of fruits and vegetables a day. For
folic acid, the recommended daily value is 400 micrograms. Good sources are citrus
fruits, tomatoes, vegetables and grain products. In January 1998, wheat flour became
fortified with folic acid to add an estimated 100 micrograms per day to the average diet.
Supplements should only be used when diet is not adequate to achieve these intakes.
The AHA Dietary Guidelines are appropriate for children older than 2 years. Children
between the ages of 2 and 5 can gradually adopt the dietary habits of the family. Like
adults, children should eat foods from all food groups, including lean meats, low-fat
dairy products, whole-grain enriched cereal products, fruits, vegetables and legumes. They
should not rely on foods containing fat or sugar substitutes, which are often of little
nutritional value. The primary emphasis of diets for children is on providing adequate
calories and nutrients for normal physical activity, growth and development.
What is homocysteine, and how is it related to cardiovascular
risk?
Homocysteine is an amino acid in the blood. Epidemiological studies have
shown that too much homocysteine in the blood (plasma) is related to an increased
risk of coronary heart disease, stroke (brain attack) and peripheral
vascular disease.
Two recent reports have strengthened the evidence for this relationship:
1. A large multi-center European trial, published in the June 11, 1997, issue of
the Journal of the American Medical Association, found that among men and women
younger than age 60, the overall risk of coronary and other vascular disease was 2.2 times
higher in those with plasma total homocysteine levels in the top fifth of the normal range
compared with those in the bottom four-fifths. This risk was independent of other risk
factors, but was notably higher in smokers and persons with high blood pressure.
2. A Norwegian study, published in the July 24, 1997, issue of the New England
Journal of Medicine, found that among 587 patients with coronary heart disease, the
risk of death after four to five years was proportional to plasma total homocysteine
levels. The risk rose from 3.8 percent in those with the lowest levels (below 9 µmol per
liter) to 24.7 percent with the highest levels (greater than 15 µmol per liter).
Other evidence suggests that homocysteine may have an effect on atherosclerosis
by damaging the inner lining of arteries, and promoting thrombosis . However, a
direct causative action has not been established.
How do folic acid and other B vitamins affect homocysteine
levels?
Plasma homocysteine levels are strongly influenced by diet, as well as genetic factors.
The dietary components with the greatest effects are folic acid and vitamins
B6 and B12. Folic acid and other B vitamins help to
break down homocysteine in the body. Several studies, including the recent multi-center
European trial, have found that higher blood levels of B vitamins are related, at least in
part, to lower concentrations of homocysteine. Other recent evidence shows that low blood
levels of folic acid are linked with an increased risk of fatal coronary heart
disease and stroke.
As yet, however, there has been no controlled treatment study showing that folic
acid supplements reduce the risk of atherosclerosis, or that taking these vitamins has an
effect on the development or recurrence of cardiovascular disease. Researchers have
studied varying amounts of folic acid to lower homocysteine levels, but it is still not
clear what an optimal dose might be and to what extent a dietary supplement might be
required to lower homocysteine levels.
Recent findings suggest that laboratory testing for plasma homocysteine levels can
improve the assessment of risk, particularly in patients with a personal or family history
of cardiovascular disease. Although evidence for the benefit of lowering homocysteine
levels is lacking, patients at high risk should be strongly advised to follow an
overall diet that ensures adequate intake of folic acid and vitamins B6 and B12.
However, this is just one risk factor. A physician taking any type of nutritional
approach to reducing a patient's risk should consider a person's overall risk factor
profile and total diet.
© 1998 American Heart Association, Inc. All rights reserved. Unauthorized use
prohibited.
The information contained in this American Heart
Association (AHA) Web site is not a substitute for medical advice or treatment, and
the AHA recommends consultation with your doctor.
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