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American Heart Association meeting report: AHA announces statement on homocyst(e)ine
DALLAS, Nov. 10 -- Citrus fruits, tomatoes, vegetables and fortified grain products which are good sources of many of the B vitamins -- are recommended "as the first line of defense" in treating elevated homocyst(e)ine, according to a new American Heart Association statement released today at the AHA scientific sessions.
Homocyst(e)ine is a natural byproduct of the body's metabolism of protein. Many studies have shown a direct relationship between the level of homocyst(e)ine and coronary heart disease. Vitamin B-6 and B-12 are also inversely associated with homocyst(e)ine.
Studies found a graded association of blood plasma homocyst(e)ine levels with cardiovascular risk. In the future, laboratory tests, which are currently not widely available to determine the level of homocyst(e)ine in blood, may improve the assessment of risk in people with a personal or family history of cardiovascular disease but who may not have other known risk factors such as high cholesterol or high blood pressure. However, the AHA does not currently advocate routine testing for homocyst(e)ine.
Although evidence for the benefit of lowering homocyst(e)ine levels is lacking, people at high risk for cardiovascular disease who also have high homocyst(e)ine levels in their blood should be advised to follow a diet based on a wide variety of foods that ensures an adequate intake of folic acid and vitamins B-6 and B-12.
"The nature of the studies to date have not been conclusive. Until there is convincing evidence of both a predictive relationship between blood homocyst(e)ine and cardiovascular disease, and a benefit of homocyst(e)ine lowering, its role will remain unproven," says Ronald M. Krauss, M.D., of the Lawrence Berkeley National Laboratory, one of the authors of the advisory.
The association recommends an increased intake of these vitamins for individuals with hyperhomocysteinemia who have had heart disease and are at increased risk for coronary heart disease because of family history of heart disease.
Additional research will be needed to determine if vitamin supplements could be considered in lieu of diet.
The intakes of folic acid, vitamin B-6 and vitamin B-12 recommended by the AHA fall within the Recommended Daily Allowances (RDA's) recently set by the Food and Nutrition Board of the Institute of Medicine, Krauss says. All are water-soluble and none are known to be toxic at the levels recommended. Taking any more than these levels "is still considered experimental." Several studies have shown that consumption of folic acid-fortified foods or multi-vitamin supplements can reduce blood levels of homocyst(e)ine.
Adequate intakes of these vitamins normally come from a healthy diet of vegetables, fruits and legumes, as well as poultry, fish, and beef. Additionally, many breakfast cereals are fortified with these vitamins. Good food sources of folic acid, or folacin include green leafy plants (foliage) from which this vitamin derives its name as well as citrus fruit and fruit juices, and legumes. The best sources of B-6 or pyridoxine are whole (but not enriched) grains, cereals, bread, liver, spinach, green beans, and bananas. B-12, or cobalamin, comes naturally only from animal sources such as liver, kidneys, meat, fish, eggs, and milk. The variations in the distribution of the wide array of B-vitamins among different food groups underscore the AHA's recommendation to choose a wide variety of foods.
"Despite abundant epidemiologic evidence for a relationship between plasma homocyst(e)ine and cardiovascular disease, and the potential for reducing homocyst(e)ine levels with increased intake of folic acid, it is not known whether reduction of plasma homocyst(e)ine by diet and/or vitamin supplements will reduce cardiovascular disease risk," the advisory warned.
"High-risk individuals should check with a dietitian about how to improve dietary intake of folic acid and other B-vitamins in order to reduce homosyt(e)ine levels," says Krauss. For some individuals who cannot or will not consume enough of the vitamin rich foods, vitamin supplements could also lower homocyst(e)ine."
Other authors of the advisory were M. RenÈ Malinow, M.D., of the Oregon Regional Primate Research Center and Oregon Health Sciences University, and Andrew G. Bostom, M.D., Memorial Hospital of Rhode Island.
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NR 98-4582 (SS98/Krauss) Media advisory: Dr. Krauss can be reached by phone at (510) 486-4277 (Please do not publish number.) qmrSS99ewskitkraussdoc.doc
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