HIGH CHOLESTEROL

High Cholesterol Center

Four kinds of fat-containing particles known as lipoproteins circulate in the bloodstream. The smallest and densest are the high-density lipoproteins (HDLs, left) which contain more protein than fat (cholesterol and triglycerides). The largest and lowest density particles are the chylomicrons (far right) which contain more fat (mostly triglycerides)

The liver releases fat-laden VLDLs into the bloodstream. VLDLs send some of their fatty triglycerides into the body’s muscles and fat tissues and the VLDLs become cholesterol-rich LDLs. The body needs LDLs for many functions but often there are more LDLs than the body needs. If so, they are deposited in the lining of blood vessels in the form of cholesterol-rich plaque, which can cause heart disease. HDLs are the garbage collectors, scooping up the cholesterol and carrying it back to the liver for disposal.

Cholesterol doesn’t simply build up on the surface of the artery. Instead, LDLs laden with cholesterol actually invade the artery wall. Next, immune cells called macrophages launch a defense, consuming the LDLs (A). These swollen macrophages become foam cells producing fatty plaque streaks and inflammation in the artery wall (B). A fibrous cap develops as the plaque matures (C). At some point, the artery wall may rupture (D), causing a blood clot to form in the artery (E), which can result in a heart attack or stroke.


What Is High Cholesterol?
What is a healthy cholesterol level? You may think you know the answer but even the experts aren’t entirely sure. As recently as 2004, a government panel changed the national cholesterol guidelines, proposing a lower target for people with a very high to moderately high heart disease risk than it had established three years earlier. The changes were based on the findings of five major heart disease prevention studies showing that the risk of heart disease decreases even as LDL ("bad") cholesterol levels drop below what was previously considered optimal.

Despite this downward trend, it’s a myth that the healthiest cholesterol level is zero. Your body needs cholesterol. Men can’t produce testosterone without it, and women can’t produce estrogen. Your intestines can’t digest food without cholesterol, and your cells can’t create their outside coating, or plasma membrane. So, cholesterol isn’t bad; it’s an important biological component. What is bad is having too much and carrying it in the bloodstream in particles that deposit it in the wrong places.

Most people’s bodies already make more cholesterol than they need, and they could stand to cut back on foods that boost cholesterol levels, such as those high in saturatedfats and trans fats, although there are exceptions to this rule.

Regardless of its source, excess LDL in your blood gets deposited in the walls of your arteries, the blood vessels that carry oxygen-rich blood to your heart and brain. The accumulation of LDL causes a narrowing and instability in the artery walls, which ultimately can lead to heart attacks and strokes.
what level of cholesterol is healthy for you, and how can you achieve it? The National Cholesterol Education Program (NCEP) has created guidelines that give you an easy, step-by-step method to evaluate your risk of heart disease, set your cholesterol goal, and take the steps you need to achieve it.

High cholesterol affects about 18% of Americans ages 20–74, and atherosclerotic heart disease is the single leading cause of death and disability in the developed world. The good news is that for most people, heart disease is preventable if you live a heart-healthy lifestyle to lower your LDL cholesterol. Exercising and eating a diet low in saturated and trans fats can help you go a long way toward reaching that goal. If you need more help, effective medications can take you the rest of the way.

High Cholesterol and Heart Disease
Keep in mind that high cholesterol isn’t the only cause of heart disease or the only characteristic that predicts an individual’s risk of developing heart disease. For instance, although the Framingham Heart Study showed that having high cholesterol is risky, it also showed that having low cholesterol doesn’t guarantee protection against heart disease. In that study, although heart disease risk was clearly greater among people with total cholesterol levels above 240 mg/dL, almost half of the people who developed coronary artery disease had total cholesterol levels below that mark, and many other people with levels above 240 mg/dL never developed coronary artery disease. (In the past, many large studies relied on total cholesterol levels because that was the only information available. Today, the NCEP guidelines de-emphasize the importance of a total cholesterol test in favor of a fasting lipid profile, a blood test that distinguishes HDL, LDL, and triglyceride levels.) While cholesterol values make useful cutoff points for comparisons, there is, as yet, no specific cholesterol level that guarantees that you will, or won’t, develop heart disease.

Diagnosing High Cholesterol
Now that you know the whys of treating cholesterol, you might be wondering how you can find out if your cholesterol needs treating. A simple blood test at your doctor’s office is the answer. The NCEP guidelines advise that all adults over age 20 have a fasting cholesterol test every five years to measure their HDL, LDL, and triglyceride levels (see Fat Particles: What’s Inside ).

The test itself is easy for patients — it involves having a tube’s worth of blood drawn from your arm during a routine visit to your physician. The preparation, however, takes a little more effort. Food and drinks affect your cholesterol profile, so you have to fast for 12 hours in order to get accurate readings of your LDL, HDL, and triglyceride levels. You also need to avoid drinking alcohol for at least 24 hours before the test. After your blood is drawn, a technician measures your total cholesterol, HDL, and triglyceride levels. Your LDL level is typically calculated from these results rather than measured directly. However, some labs now routinely measure LDL directly using newer technology.

Problems with accuracy. The results from cholesterol tests sound quite precise, but the exactness of the numbers can mask a fair amount of uncertainty in the testing process. This might reflect the method by which the sample is prepared, the purity of the chemicals added to it, the quality or performance of the machine used to analyze the sample, or the skill of the person doing the lab analysis. For example, if your triglyceride level is above 400 mg/dL, the calculation cannot be performed accurately, and you will have to have the LDL measured by a different method to obtain a result.

Inconsistencies over time. Another source of inconsistency is biological variability, or the natural variations in the amount of cholesterol in a person’s blood at any moment. Changes in your average daily levels may reflect diet, smoking, illness, weight change, exercise, or certain medications. The number on the laboratory report reflects the level at a single point in time. One study showed that total cholesterol levels can fluctuate by as much as 11% over the course of a year. The researchers estimated that 60% of that variation was caused by biological fluctuations, and the remaining 40% by variations in the test itself. That same study found that triglyceride measurements can vary anywhere from 13% to 41%, and HDL levels from 4% to 12%. What all this means is that a small change in your cholesterol level from one test to another does not necessarily represent a real gain or loss — and an unusually high or low level may be a fluke.

The NCEP has crafted standards designed to minimize variability and expects laboratories to follow guidelines that ensure only a 3% margin of variation in measuring total cholesterol.

What you can do. You can do something about biological variability. For routine total cholesterol measurements, try to have your blood drawn at the same time of day each time you have the test — and follow a similar eating, exercising, and medication-taking pattern. You can also improve the accuracy of a cholesterol test by not drinking alcohol for several days beforehand, sitting for at least five minutes before your blood is taken, remaining seated during the procedure, and informing your doctor of any fevers you’ve had recently or medications you’ve taken. Then, you and your physician can make an informed decision about the best way to bring any wayward cholesterol levels back in line.

In any case, one test is clearly not a solid basis upon which to make important decisions about therapy. If your doctor suggests drug therapy based on a cholesterol test, ask for a second test to double-check the results.