Diet and heart disease: a stronger link?

Investigation into the relationship between diet and heart disease are limited by ethics and expense: Researchers can't very well have one group of people eating lots of cholesterol-laden food for decades and maintain antoerh group on a low-cholesterol diet. By quilting together animal studies, epidemiological research and small-scale or otherwise limited human experiments, scientists have hypothesized a link, but debate continues (SN: 12/22 & 29/84, p. 390).

Two studies in the March 28 NEW ENGLAND JOURNAL OF MEDICINE come down on the side of such a link, but neither alone is likely to be the final word.

In one study from Leiden University in the Netherlands, 39 men with at least one coronary artery choked to less than half its diameter by cholesterol deposits were placed on vegetarian diets to lower cholesterol levels in their blood. After two years, X-ray studies of their hearts revealed no increased obstruction in 18 of the 39 men, which, the researchers reports, indicates that "dietary intervention may reduce the rate of coronary lesion growth."

Since the study involved snaking a catheter into the heart to assess the blockage -- a procedure that carries a small risk -- no control group was followed. The researchers admit that this limits the usefulness of the study. In an accompanying editorial, David H. Blankenhorn of the University of Southern California in Los Angeles notes the same lack but observes that the study "provides the only direct information we have relating a defined diet to measured changes in coronary lesions."

The second report involved 1,001 middle-aged men in the Ireland-Boston Diet-Heart study, a novel data base that includes men in Ireland, brothers of these men who moved to Boston, and Boston sons of Irish immigrants.

The three groups had about the same rate of heart disease-related death. However, when the researchers looked back at 20-year-old records of what the men had said they were eating at the study's outset, they found that those men with high-cholesterol diets -- wherever they lived -- were more likely to develop heart disease. The finding, conclude the scientists from Harvard University in Boston and Trinity and University colleges in Dublin, "supports the hypothesis that diet is related, albeit weakly, to the development of coronary heart disease."

The Ireland-Boston study shows that equations taking into account how much and what kinds of food are eaten are as predictive of heart disease as is smoking, Blankenhorn told SCIENCE NEWS.

Other researchers, who had not yet seen the reports, were unwilling to comment on ptheir importance. But W. Virgil Brown, an atherosclerosis expert at the Mt. Sinai School of Medicine in New York, when told some of the details of the Dutch study, said, "I would be very hesitant to make too much of that."

The studies, notes Blankenhorn, "support the need for a change in the national diet and indicate merit for vegetarian diets." But, he observes, "there is sufficient acknowledged weakness in both studies to provide grounds for rebuttal by dedicated meat eaters and oponents of a national diet change." Stay tuned.