Q: Is it true that taking folic acid and other B vitamins may protect me from having a heart attack?
About 30 years ago, doctors recognized that people with a rare genetic disorder called homocystinuria frequently died at a young age of a heart attack or stroke.
Homocystinuria is due to a metabolic defect that leads to extremely high blood levels of the amino acid homocysteine.
Although the mechanism is not clear, markedly increased levels of homocysteine are associated with premature arteriosclerosis and blood clot formation, which together lead to narrowing and even complete blockage of arteries supplying the heart, brain and other organs. Three vitamins -- folic acid and vitamins B-6 (pyridoxine) and B-12 -- are required to maintain normal levels of homocysteine by converting it to other amino acids.
Recent population studies have found that people with even slightly elevated blood levels of homocysteine are at somewhat greater risk of having a heart attack.
Therefore, researchers were wise to examine the relationship between homocysteine levels of and the degree of narrowing of the carotid arteries (arteries in the neck supplying blood to the brain) as well as the dietary intake and blood concentrations of the three vitamins.
In a study of 1,041 subjects from the Framingham Heart Study, the scientists found that the likelihood of carotid artery narrowing was twice as great in both men and women with the highest blood concentrations of homocysteine as compared to those with the lowest levels.
In addition, individuals with the highest blood levels of homocysteine had the lowest intakes and blood concentrations of folic acid and pyridoxine.
Keep in mind that much more work is needed before it is known that lowering homocysteine levels would be beneficial. You also know that a doctor cannot measure your homocysteine level to see if it is high enough to increase your risk, because the test is available only in a few research laboratories.
The best bet is to be sure that you are getting adequate amounts of folic acid and vitamin B-6, the vitamins best correlated with higher levels of homocysteine.
Eat plenty of foods that are rich in these vitamins. Good sources of folic acid include citrus juices, beans, whole grains, leafy vegetables and broccoli. Vitamin B-6 is found in whole and fortified grains, beans, nuts, bananas, meat, poultry and fish.
Should you be taking vitamin supplements in case your homocysteine levels are high and your diet is deficient in these foods?
It is safe to take a vitamin supplement containing 1 or 2 milligrams of folic acid and 2 milligrams of vitamin B-6. Larger doses are not necessary; in fact large doses of folic acid can be dangerous because they could mask the early signs of pernicious anemia.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.