August 26, 2002
Copper May Be Behind Legumes' Heart-Healthy Properties
GRAND FORKS, N.D.--Increased dietary copper through legumeconsumption may protect against heart disease, according to an editorialpublished in the Aug. 12 issue of the Archives of Internal Medicine (162,15:1780-1, 2002) (http://archinte.ama-assn.org).In her editorial, Leslie M. Klevay, M.D., S.D.(Hyg), a researcher at the U.S.Department of Agriculture's Human Nutrition Research Center, discussed the FirstNational Health and Nutrition Examination Survey Epidemiologic Follow-Up Study (ArchInt Med, 161, 21:2573-8, 2001), in which researchers from Tulane UniversitySchool of Public Health and Tropical Medicine in New Orleans identified areduced risk of coronary heart disease with increased legume consumption. TheTulane researchers concluded legumes protected against heart disease because ofthe possible protective properties of calcium, fiber, folate, magnesium,potassium or vegetable protein, but Klevay believes copper is the heart-healthynutrient.
In reviewing research on copper and heart disease, Klevay noted copperdeficiency affected numerous characteristics: 1) it elevated cholesterol, bloodpressure and uric acid; 2) it adversely affected electrocardiograms; 3) itimpaired glucose tolerance; and 4) it promoted thrombosis and oxidative damage.Of the nutrients the Tulane researchers cited as possibly protective, fiber andmagnesium have single effects on cholesterol levels or electrocardiograms, butthey do not have effects on several characteristics simultaneously, according toKlevay.
Klevay cited research on the copper content of legumes, of which soy and limabeans ranked in the upper tertile of 235 foods for copper content. Diets low incopper may explain much of the epidemiology and pathophysiology of ischemicheart disease, according to Klevay.
The Tulane study demonstrated those with more frequent legume intakedemonstrated lower systolic blood pressure, less hypertension, lower levels oftotal cholesterol and hypercholesterolemia, and less diabetes, in spite ofhaving eaten more fat. Klevay attributed this effect to increased copperconsumption, as previous animal research demonstrated a high-fat diet producedcardiovascular lesions in mice only when copper intake was insufficient.
In her conclusion, Klevay stated copper supplements have improved oxidativedefenses in middle-aged people, and although increased copper intake fromlegumes was considerably less than what is found in supplements, the lower dosemay have been effective because of the longer duration of supplementation of amuch larger population.
"While many constituents of legumes may play a role in decreasing therisk of cardiovascular disease, evidence from prospective studies support theroles of fiber, folate, potassium, calcium and magnesium in decreasing risk ofcardiovascular disease," wrote Linda Bazzano, Ph.D., the lead researcher onthe Tulane study, in reply to Klevay's conclusions. "Moreover, randomizedcontrolled trials show that soybean protein reduces serum total and low-densitylipoprotein cholesterol levels, and that potassium supplementation lowers bloodpressure. Such evidence is not available for dietary copper."
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