In the normal course of events, the homocysteine that healthy people manufacture is converted into amino acids that do them no harm. This is accomplished by three B vitamins--B-6, B-12, and, probably most important, folacin (also called folate or, when used in a supplement or to fortify foods, folic acid). If the conversion does not take place rapidly enough, due to a genetic defect or vitamin deficiency, elevated levels of homocysteine may, the theory goes, damage arterial walls and promote the buildup of cholesterol, thus potentially leading to arterial blockage and a heart attack.
It took years for researchers to recognize the importance of Dr. McCully's finding. Homocysteine is now on its way to being a household word, like cholesterol. But doctors, as well as the public, are still unsure what they should do about it.
Many studies, no certainties
An impressive number of new homocysteine studies have appeared in the past decade, and some have found that a high level of homocysteine is an independent risk factor for heart disease, along with high blood pressure and high blood cholesterol. In 1992, for example, a large study found that men with homocysteine levels in the top 5% were at three times the risk for heart attack as those with lower levels.
A study in 1997 showed that high levels increased the risk of death in those who already had heart disease. One study of 1,500 men and women in 19 European medical centers found that those who ranked in the top 20% for homocysteine levels had double the risk of heart disease, compared to those with low homocysteine--similar to the increased risk from smoking or high cholesterol. But people in the study who took supplements of folic acid, B-6, and B-12 cut their risk substantially. A study in Circulation found a link between heart disease and high homocysteine levels in young women--a group in which heart attacks are rare--particularly when the women were deficient in folacin. This is just a sample of the findings.
The evidence, however, is not consistent. One study conducted at the Harvard Medical School did not find that elevated homocysteine levels increased the risk of arterial narrowing. And other good studies have failed to identify high homocysteine levels as an independent risk factor for heart disease.
Some people wonder if high levels might be the result, rather than the cause, of heart disease. It's apparent that low blood levels of folate and vitamin B-12 (and to a lesser extent B-6) are associated with high homocysteine levels and that increasing your intake of these vitamins can lower homocysteine. What's still unknown is whether consuming B vitamins also reduces your risk of heart disease. Evidence is mounting, and studies are now underway, but it will take time to come up with the answer.
Too early to be tested
You may be wondering whether you should have your homocysteine level measured. In fact, unless you have a family history of early heart attacks or have already had a heart attack and your doctor wants to check your level, you don't need to have it measured. The problem is that there's no clear definition of normal or desirable levels.
Another problem: it remains to be proven that lowering high homocysteine levels will actually reduce the risk of heart attack and stroke (except in those with homocystinuria). Thus homocysteine has not "replaced" cholesterol as a health concern. (Don't go back to cream and butter!) The homocysteine theory fills in some blanks in the puzzle. For example, many people with coronary artery disease don't have high blood cholesterol levels, but may have high homocysteine.
No need to wait for certainties
What you can do, without getting any test and without hesitation, is to increase your consumption of B vitamins. If you eat well, and particularly if you consume fortified foods, you can get all these vitamins from your diet.
Folacin and B-6 present few problems: they are plentiful in leafy greens, whole grains, some fruits, and fortified breakfast cereals. Cereal grain and white flour (breads, pasta, grits, white rice, and cornmeal) are now fortified with folic acid--chiefly because folic acid is important in preventing certain birth defects. A good target is at least 400 micrograms daily, especially for women of child-bearing age. (No one knows if such levels of folic acid intake are enough to reduce the risk of heart disease, but they can't hurt.)
Vitamin B-12 does present some concerns: it is found chiefly in meat, organ meats, eggs, and other foods that tend to be high in cholesterol and saturated fat (definitely not good for the arteries). But fortified cereals, fish, lean meats, and milk do supply vitamin B-12. The chart below will guide you.
If you don't eat at least five fruits and vegetables a day, as well as fortified cereals and small servings of lean meat, poultry, or fish, do consider taking a daily multivitamin supplement providing 100% of the RDA of these B vitamins.
The folic acid and B-12 in supplements and fortified foods are much better absorbed by the body than the folacin and B-12 found naturally in food. Thus, recent studies have shown that people who take folic acid supplements decrease their homocysteine levels more than those who get more folate from food.
Keep in mind: Only a comprehensive program can prevent heart disease: not smoking; eating a diet rich in fruits, whole grains, fortified foods, and vegetables, and low in animal fats; and regular exercise such as brisk walking. Regular checkups for blood pressure and blood cholesterol are important, too.
|Folacin||400 micro-grams (mcg)||Leafy greens, broccoli, wheat germ, beans, whole grains, fortified oatmeal. 1 cup cooked spinach has 260 mcg; 1 cup beans, 160 to 350 mcg.|
|B-6||1.3 milligrams (mg), women; 1.7 mg, men||Whole grains, bananas, potatoes, beans, fish, meat, poultry. 1 medium potato (baked, with skin) or banana has 0.7 mg.|
|B-12||2.4 mcg||Meat, poultry, liver, eggs, dairy, fish, fortified cereals and soy products. 3 oz beef has 2 mcg; 1 cup milk, 0.9 mcg.|