Diet Debate

Is cholesterol the culprit?

Scrambled eggs and bacon for breakfast. A cheeseburger and French fries for lunch. A slab of roast beef and a sour cream-topped baked potato for dinner Typical of the American lifestyle, such fatty, cholesterol-rich foods have long been cited by doctors as the primary cause of coronary artery disease, the nation's No. 1 killer. To keep the arteries unclogged, they have been urging a diet low in fats, stressing vegetables, poultry and fish over beef, eggs and dairy products.

The vigor of their message has tended to obscure the fact that the "diet-heart hypothesis," as the cholesterol link with coronary disease is known, remains a theory and the subject of heated debate. True, studies have established that high cholesterol levels in the blood are associated with increased heart disease. But, admits Dr. Basil Rifkind, chief of the lipid metabolism branch of the National Heart, Lung and Blood Institute, "what's missing is the proof that you can prevent heart disease by reducing cholesterol. "

Critics such as Vanderbilt's Dr. George Mann point out that most cholesterol in the blood does not come from foods directly but is produced by the body Diets and drugs can lower cholesterol levels no more than 40%--not enough, they claim, to affect the rate of heart disease heart attacks. Some doubt that cholesterol is the main culprit, regardless of its origins. Lately they have been pon dering alternate theories, among them:

Homocysteine Vitamin B6 Hypothesis.

Proposed in 1969 by Pathologist Kilmer McCully, then of Harvard, this thesis also implicates diet, but the villain is protein. Methionine, an amino acid, is broken down by the body into homocysteine, a chemical that promotes atherosclerosis (or the buildup of plaque in the arteries) in lab animals. According to the theory, it is converted by vitamin B6 into an innocuous byproduct, but if there is a deficiency of B6, homocysteine piles up in the blood and causes atherosclerosis. In the view of the theory's proponents, Americans are vulnerable to heart disease because the protective vitamin, which is found in meats, fruits and vegetables is destroyed by cooking and canning.

Herpes Virus Hypothesis.

This challenging theory holds that atherosclerosis results from infection by the ubiquitous herpes viruses. At Cornell's College of Veterinary Medicine, Microbiologist Catherine Fabricant and colleagues are working with a herpes virus that produces in chickens a variety of tumors known as Marek's disease. The scientists found that it also causes atherosclerotic lesions in heart arteries. But, intriguingly, virustree chickens do not develop heart disease even when fed a high cholesterol diet. Fabricant speculates that something similar may happen in humans as well.

No one can say for sure whether either of these theories will eventually replace the cholesterol-heart link. Most doctors still believe a combination of factors brings on heart disease, and will prudently continue to recommend low cholesterol diets, plenty of exercise and no smoking Warns Dr. William Castelli, director of the pioneering Framingham, Mass., heart studies: "If people think they can go out and eat all the hamburgers and hot dogs they want and be safe by taking vitamin B6, they're crazy."

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