Cholesterol: Get Your Fats Straight
9/8/2010
If you associate cholesterol with excess weight, fried foods and an increased risk of suffering a heart attack or stroke-as most Americans do-you're right. But that's only one over-simplified part of a complex story.
Cholesterol is a wax-like substance needed by the body to build cell walls and make hormones. Your liver is constantly producing cholesterol regardless of what you do, but levels in your blood are sometimes increased by lifestyle measures, such as a diet that's high in the wrong kind of fats. Over an extended period too much cholesterol in the blood stream can lead to fatty deposits on the walls of arteries, the first step in the development of heart disease.
That's why, as routine, preventive practice, doctors frequently ask patients to get a blood test measuring cholesterol and other lipids (or fats) in the blood. Known as a lipid profile, this test renders valuable information about an individual's risk of heart disease.
If you're like most Americans, what you remember about your cholesterol is probably a three-digit number-your total cholesterol. And it's a handy number to keep in mind.
If your total cholesterol creeps over 200, you should start being concerned; and if it's over 239, your doctor has probably talked to you about things you should do, including the use of cholesterol-lowering medications.
Total cholesterol is a rough measure of what's taking place in your blood vessels, but, in interpreting the results, your doctor is more concerned about other components of the profile.
Two of these components, known as "good" and "bad" cholesterol, are lipoproteins-special proteins that act as couriers in the blood stream, delivering cholesterol to wherever it's needed.
As an analogy, think of HDL (high-density lipoprotein) as highly fit bike riders, powering themselves efficiently through the arteries. LDL (low density lipoproteins), on the other hand, are loosely formed blobs that float like sponge toys on the surface of a bath tub.
LDL is "bad" cholesterol because it tends to collect, making fat deposits that block the normal flow of blood. HDL is "good" because it gathers up excess LDL particles and carries them back to the liver to be removed from the body.
According to guidelines of the National Cholesterol Education Project (NCEP), an HDL level above 60 mg/dL is desirable and considered protective against heart disease. A level under 40 mg/dL, on the other hand, is a risk factor, even if other components of the profile are normal.
For most individuals, an LDL under 130 is recommended, but persons diagnosed with heart disease or diabetes are advised to keep LDL levels under 100 mg/dL.
One of the most important measures of cardiovascular health is the ratio of total cholesterol to HDL. James' total cholesterol of 201 with an HDL of 75, for example, yielded a ratio of 2.7-considered very low risk, despite the moderately elevated total cholesterol. The NCEP recommends a ratio under 4.5.
Another fat usually measured in a lipid profile is triglyceride. Triglyceride levels under 150 mg/dL are considered desirable, and recent research indicates that high triglycerides are a risk factor even when other parts of the lipid profile are normal.
Most preventive and treatment strategies focus on lowering LDL and total cholesterol. Yet studies show that increasing HDL-even with no corresponding decrease in LDL-may be at least as effective.
While a traditional low-fat diet will lower LDL and total cholesterol, it may also lower HDL, particularly if carbohydrates are substituted for the fats. More recent approaches advocate not just eliminating saturated fats but replacing them with fruits, vegetables, whole grains and monounsaturated fats. Found in olive and canola oil, almonds, walnuts and avocados, monounsaturated fats will maintain or increase HDL levels while providing beneficial nutrients. Other ways to boost HDL include weight loss, regular exercise of at least moderate intensity, smoking cessation and moderate use of alcohol.
Among cholesterol-lowering medications, statins bring about a 10 to 15 percent increase in HDL while reducing LDL by 30 to 50 percent. Niacin may be the best treatment for increasing HDL, and fibrates are the treatment of choice for high triglycerides.
In diagnosing, preventing and treating heart disease, doctors know they have much left to learn. For now and the foreseeable future, however, there's no question that cholesterol-in all its ramifications-will continue to play a major role.