QUESTION: Last week I answered a question about heart disease by reviewing some studies that showed a reversal of the disease process associated with dietary changes, drugs and stress reduction. This week, I would like to continue the discussion about this important issue.

There is no question that coronary artery disease is a major problem; 7 million people in the United States have the disease and more than a half million people die from heart attacks each year. The question is, what can be done to avoid the disease? The answer usually relates to dietary changes or drug treatment to lower blood levels of cholesterol.The earliest guidelines probably originated from the American Heart Association, which has been warning Americans for years to restrict the amount of fat in the diet, especially saturated fat. These guidelines have been reinforced many times by various professional and government groups.

For instance, a little more than a year ago, the U.S. surgeon general issued a major report on nutrition and health. In this report, supported by many research studies, was a recommendation that all Americans "reduce consumption of fat (especially saturated fat) and cholesterol."

A later report by the National Heart, Lung and Blood Institute's National Cholesterol Education Program (NCEP) made basically the same recommendations but actually changed the levels of total cholesterol considered safe from 240 milligrams (mg per deciliter of blood) to 200 mg. Levels from 200 to 239 were considered "borderline high," and more than 240 mg as "high risk."

Under the NCEP guidelines, the first step in the treatment of high cholesterol would be diet guidelines similar to the American Heart Association guidelines (less than 30 percent fat). If this approach didn't work, saturated fats were to be reduced to less than 7 percent. As a last resort, cholesterol-lowering drugs were to be used.

The question is, does lowering fat in the diet decrease the risk of having heart disease? Population studies show that high fat intake is associated with higher levels of heart disease. Examples of these populations are Finland, the Netherlands and the United States, where saturated fat levels are about 22 percent of total intake and coronary artery disease is high.

On the other hand, Seventh-day Adventists, who follow a vegetarian diet, have a rate 50 percent below the general population. However, population studies have limitations because many populations have many other differences besides the diet.

Clinical trials in which the diet is manipulated to lower the fat intake show only about a 10 percent reduction in blood cholesterol and confusing results in terms of outcome. Part of the problem relates to the study design and part to the limited time frame for most of these studies.

Drug studies have shown a more consistent effect. Using the drug cholestyramine in a large group of middle-aged men showed a 19 percent reduction in the number of heart attacks over a seven-year period. Another study using gemfibrozil showed a 34 percent decrease in coronaries over the control group. But it is still unclear if the results of these studies can be generalized to women and older persons. Another question relates to changing the diet of children.

Next week I'll finish the discussion and give some prudent guidelines that can be followed by anyone.