Low cholesterol's value outstrips risk


October 06, 1992|By Dr. Simeon Margolis | Dr. Simeon Margolis,Contributing Writer

Q: All the publicity about the risks of a high cholesterol count for heart disease have made me very happy that my careful dietary habits have always kept my cholesterol close to 150. Now I have read there may be some danger from having a cholesterol level that is too low. Would it be a good idea for me to follow a less rigid diet so my cholesterol would be higher?

A: No! Newspaper headlines recently trumpeted some findings from the MRFIT study which reported a cholesterol level below 160 mg/dl was associated with a higher death rate from several causes. To appreciate the real meaning of these findings, it is necessary to understand how the results were obtained.

The report was based on a study of the cause of death in about 351,000 men who were followed for 12 years after a single cholesterol measurement was obtained when they were age 35 to 57. The studyshowed the higher the cholesterol, the greater the number of deaths from cardiovascular disease, which was the most common cause of death in these men. This extremely important result, which duplicates the findings of many other investigations, was glossed over in the newspaper articles.

The authors also reported that cholesterol less than 160 mg/dl was associated with a significantly increased risk of death from certain types of cancer, cirrhosis of the liver, suicide, alcohol dependence and obstructive lung disease. It is crucial to recognize the association of a low cholesterol with a higher death rate from a disease, such as cirrhosis of the liver, does not prove a low cholesterol causes the disease.

In fact, it is very likely that some of the disorders, present at the time the cholesterol was measured, were the cause of the low cholesterol. Thus, individuals with alcohol dependence, the cause of cirrhosis and a frequent contributor to suicide, often are poorly nourished and have a low cholesterol.

Similarly, the poor nutritional state of depressed people (another forerunner of suicide) and the weight loss that accompanies cancer and chronic lung disease are known to lower the cholesterol level. As a consequence, it is likely that many of the men with cholesterol values less than 160 mg/dl had these low levels because they already had cancer, chronic lung disease, alcohol dependence or depression -- and so it is no surprise that a low cholesterol was subsequently associated with a higher death rate from these disorders as well as suicide.

While it is still possible that a low cholesterol does cause some diseases, this study certainly offers no proof for that notion. In addition, the clear benefits of a low cholesterol in preventing cardiovascular disease far outweigh any potential dangers of its role in causing these other, much less common, causes of death.

Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine and associate dean for faculty affairs at the school.

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