Cardiology: Four Fats in the Blood: Which Cause Heart Attacks?

Every week for the past year, more than 1,100 couples in five U.S. cities have selected a seven-day supply of food from a carefully drawn list and then sent their orders to Washington. Processed by a computer, the orders go back to shipping offices in the five cities, and the food is delivered. Container labels give no clue to the precise ingredients in such items as salad dressings, cake mixes and milk concentrates.

The computerized menus represent no attempt to automate a housewife's traditional chore. They are part of a serious and important study, financed by the U.S. Public Health Service, designed to discover whether American men still in their prime can be saved from fatal heart attacks by changes in their diet.

The computer's coldly calculated answers promise to help cut through the growing confusion about fats and the heart. Today, almost every time some authority sounds off on the subject, the effect is to multiply the contradictions. Last week the American Heart Association suggested that although the proof is not yet conclusive, the weight of evidence indicates that a lower-fat diet, with proportionately more polyunsaturated:|: vegetable fats, will help to save lives. But the Food and Drug Administration had just threatened action against manufacturers who label shortenings and cooking oils as polyunsaturated, thus implying that they are good for the heart and arteries.

Easy to Measure. Atherosclerosis that narrows or closes the heart's coronary arteries with slushy, fatty deposits is the greatest killer in the U.S., where it claims 500,000 lives a year, twice as many as cancer. The death rate from prime-of-life heart attacks goes up, roughly, with the concentration of fats in the blood. Most biochem ists divide these circulating fatty substances into four groups: cholesterol, fatty acids, phospholipids, and triglycerides, some of them "free," some of them combined with proteins or with one another.

It is not yet certain which of them are the most important in causing atherosclerosis. But cholesterol has received the widest publicity, largely because it is the easiest to measure and thus be comes a handy guide to arterial and coronary health. Among peasants in India, starved of protein and of fat, a cholesterol level of 125 milligrams per 100 milliliters of blood is common. It is about the same for fish-and-rice-eating Japanese. Among Americans living high off the hog, it hits 250 before a doctor begins to worry. And among men with coronary-artery disease, it may go to 500 or more.

The squishy, fatty nature of the deposits in clogged arteries has been recognized for more than 200 years, and the presence of cholesterol (from the Greek for bile solids) in the deposits has been known for more than a century. Presumably the cholesterol is deposited from the blood. Just how or why, no one knows. But high levels of circulating cholesterol go with a high incidence of heart attacks in men 45 to 65; doctors have spent years trying to figure out why the cholesterol piles up.