Understanding Cholesterol

by Food and Drug Administration (FDA)

Just as Americans all over the country were cutting out doughnuts as a breakfast staple and ice cream as a routine nighttime snack, a journalist published a book that called the benefits of eating less fat a "myth." Next, scientific studies endorsing the value of low blood cholesterol reported that eating oat bran and olive oil may not be a panacea for those worried about heart disease. Suddenly, what had seemed a direct disease prevention message became a complicated issue. The debate about cholesterol — whether to lower it and how to lower it — was on.

Killer Disease

Despite impressive declines in mortality rates over the past 20 years, coronary heart disease remains the leading cause of death in the United States. It is the number one killer of both men and women, claiming more than 500,000 American lives each year.

In 1985, the National Heart, Lung, and Blood Institute launched the National Cholesterol Education Program (NCEP) to reduce death and disability from heart disease by controlling high blood cholesterol. Blood cholesterol is a substance that travels through the body and deposits fatty streaks in the inner linings of the arteries.

"The evidence relating diet (including saturated fatty acids and dietary cholesterol — a fat-like substance contained in animal foods) — to blood cholesterol levels and coronary heart disease is compelling," NHLBI says, citing a variety of animal and human studies.

In a pamphlet sent to doctors in November 1987, NCEP recommended that physicians advise patients to have their blood cholesterol checked every five years (more often if it is found to be high) and to eat a healthful diet, low in saturated fat and dietary cholesterol. (See "Do You Know Your Cholesterol Level?" in the March 1989 FDA Consumer)

However, journalist Thomas J. Moore, in his book Heart Failure, takes issue with the need for such a program. According to Moore, a series of government heart disease studies have been an "extravaganza put on" by the "medical elite." The relationship between diet and coronary heart disease is "tenuous at best," says Moore. But, what he called "a medical version of the military-industrial complex" has eaten up an enormous amount of federal funds to convince the public that changing the diet will reduce heart disease.

Since 1948, NHLBI researchers have reviewed the cholesterol levels, living habits, and diet of 5,127 adults in Framingham, Mass. During this study, scientists have demonstrated a link between high blood cholesterol levels and increased heart disease. However, Moore maintains that the study has failed to show a link between diets high in cholesterol and heart disease.

Yet, other studies have established a dietary connection, although smaller than expected. In the seven-month-long Heart-Diet Pilot, conducted in 1968 by researchers from the University of Minnesota, participants who ate less cholesterol and saturated fat and more polyunsaturated fat lowered their blood cholesterol levels 10.5 percent.

Reinterpreting or Misinterpreting?

To bolster his arguments, Moore points to the 10-year Multiple Risk Factor Intervention Trial conducted by NHLBI. Most of the 12,866 men in the study smoked cigarettes, were obese, and ate a diet with more than twice the recommended amount of cholesterol. They were divided into two groups. One entered an extensive fitness and diet program, and the other received no special program. After seven years, researchers found no significant difference in the number of deaths due to heart disease among the men. "The trial failed completely," Moore says.

But, Timothy Johnson, M.D., medical editor of ABC News and the first editor of the Harvard Medical School Health Letter, sees the results from this trial differently. For instance, he writes in the Harvard Medical School Health Letter, "telling the control subjects about their high-risk status and sending them back to their own physicians with that information led to efforts to reduce their risk." The fact that the number of coronary deaths was 40 percent less than expected in both groups leads Johnson to conclude that "the reason the two groups didn't differ much was that the controls, like the subjects, changed."

Moore questions the credibility of other studies. In 1984, NHLBI selected nearly 4,000 middle-aged men with high blood cholesterol to participate in the large-scale Coronary Primary Prevention Trial. All were placed on diets low in fat and cholesterol. Then, half the men were instructed to drink twice daily a mixture of water and cholestyramine, a drug expected to lower blood cholesterol. After seven years, the group treated with the drug showed an 8 percent reduction in blood cholesterol. Another failure, according to Moore. NHLBI anticipated a 28 percent reduction.

NHLBI, however, has another explanation. The drug had unpleasant side effects, including constipation, gas and heartburn. Many of the men were unable to follow the prescribed regimen. The men who took the full dose of the medication reduced their cholesterol by 25 percent and experienced almost 50 percent fewer heart attacks and deaths from heart disease than the placebo group. And, Moore fails to point out that the men who lowered their blood cholesterol the most suffered fewer heart attacks than those in the placebo group.

Filling in the Holes

"Science can't answer all the questions," says Susan Okie, M.D., a Washington, D.C., physician and journalist. A skeptic can easily identify the holes and translate promising findings into negative ones.

"No scientific outcome is ever unanimous," the American Heart Association (AHA) explains. Nevertheless, AHA and NHLBI summarized the cholesterol research in response to Moore to show that scientific evidence makes an undeniable case that intervention to lower blood cholesterol — by diet or, when necessary, by medication — reduces the risk of coronary heart disease.

Research results published since the September 1989 release of Moore's book continue to strengthen the argument for eating a diet low in saturated fats. In a study described in the March 23 issue of the Journal of the American Medical Association, researchers from the Atherosclerosis Research Institute at the University of Southern California School of Medicine were able for the first time to link the consumption of saturated fatty acids with the growth of new coronary lesions. In a March 1 article in the New England Journal of Medicine, Columbia University researchers reported that healthy college-aged men who ate a low-fat diet for 10 weeks lowered their blood cholesterol levels by 8 percent. Based on available evidence, say experts such as Richard Peto of Oxford University, a 1 percent reduction in blood cholesterol level diminishes the risk for coronary heart disease by approximately 2 percent.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.