Can your LDL cholesterol be too low?

The current guidelines for preventing heart attacks recommend that healthy people get their blood levels of the bad LDL cholesterol below 100, and that those who have had heart attacks get their LDL below 70.

However, cholesterol is a necessary part of surface membranes in your body and also functions in making many different chemicals in your body, so there is concern whether you can drive your LDL cholesterol low enough to harm you. You lower LDL cholesterol by taking certain drugs or eating a diet that restricts saturated and partially hydrogenated fats and refined carbohydrates. A study from Harvard Medical School shows that most people should try to get blood levels of the bad LDL cholesterol as low as possible (Journal of the American College of Cardiology, October 2005.) The participants who lowered their LDL cholesterol the most had the fewest heart attacks and strokes and did not suffer any obvious bad side effects.

You can remember that HDL is the good cholesterol by thinking "H is for healthy"; and that LDL cholesterol is bad because "L is for lousy". The good HDL cholesterol carries cholesterol from your bloodstream to your liver where it can be removed from your body. The bad LDL cholesterol carries cholesterol to your arteries where it forms plaques.

To some degree, your good HDL cholesterol protects you from the bad LDL cholesterol, so having a high level of the good HDL helps to protect you from having a heart attack from high levels of the bad LDL. However, this is sometimes not true. Some people with very high blood levels of the good HDL cholesterol still get heart attacks. Hence the guidelines now are based purely on blood levels of the bad LDL cholesterol.

A heart-healthy diet can lower cholesterol levels in most people. You can lower your LDL cholesterol by restricting your intake of saturated and partially hydrogenated fats, refined carbohydrates and calories.

Gabe Mirkin, M.D.

Dr. Gabe Mirkin has been a radio talk show host for 25 years and practicing physician for more than 40 years; he is board certified in Sports Medicine and three other specialties.

Dr. Mirkin's daily features on fitness have been heard on CBS Radio News stations since the 1970's. He has written 16 books including The Sportsmedicine Book, the best-selling book on the subject that has been translated into many languages. His latest book is The Healthy Heart Miracle, published by HarperCollins.

Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. A Boston native, Dr. Mirkin did his residency at the Massachusetts General Hospital. He has served as a Teaching Fellow at Johns Hopkins Medical School, Assistant Professor at the University of Maryland, and Associate Clinical Professor in Pediatrics at the Georgetown University School of Medicine. He has run more than forty marathons and is now a serious tandem bicycle rider with his wife, nutritionist Diana Mirkin.