Cholesterol and heart disease

Doctors measure your cholesterol level by taking a sample of blood and counting the milligrams of cholesterol in 1 deciliter (%) liter) of blood. When you get your annual report from the doctor, your total cholesterol level looks something like this: 225 mg/dl. Translation: You have 225 milligrams of cholesterol in every tenth of a liter of blood. Why does this matter? Because cholesterol makes its way into blood vessels, sticks to the walls, and forms deposits that eventually block the flow of blood. The more cholesterol you have floating in your blood, the more cholesterol is likely to cross into your arteries, where it may increase your risk of heart attack or stroke.

oj^NG.' As a general rule, the National Cholesterol Education Program (NCEP) says that for adults, a cholesterol level higher than 250 mg/dl is a high risk factor for heart disease; between 200 mg/dl and 250 mg/dl is considered a moderate risk factor; below 200 mg/dl is considered a low risk factor.

Cholesterol levels alone are not the entire story. Many people with high cholesterol levels live to a ripe old age, but others with low total cholesterol levels develop heart disease. Worse yet, recent research indicates that low cholesterol levels may increase the risk of stroke. In other words, cholesterol is only one of several risk factors for heart disease. Here are some more:

I An unfavorable ratio of lipoproteins (see the following section) I Smoking I Obesity

I Age (being older is riskier) I Sex (being male is riskier) I A family history of heart disease

To estimate your own risk of heart disease/heart attack, check out the NCEP heart attack risk calculator at hin.nhlbi.nih.gov/atpiii/calculator. asp.

Cholesterol season

Even if you allow yourself to indulge in (a few) high-cholesterol ice cream cones and burgers every day of the year, your cholesterol level may still be naturally lower in the summer than in winter.

The basis for this intriguing culinary conclusion is the 2004 University of Massachusetts SEASONS (Seasonal Variation in Blood Lipids) Study of 517 healthy men and women ages 20 to 70. The volunteers started out with an average cholesterol level of 213 mg/dl (women) to 222 mg/dl (men). A series of five blood tests during the one-year study showed an average drop of 4 points in the summer for men and 5.4 points for women. People with high cholesterol (above 240 mg/dl) did better, dropping as much as 18 points in the summer.

U. Mass cardiologists say one explanation for the summer downswing may be the normal increase in human blood volume in hot weather. Cholesterol levels reflect the total amount of cholesterol in your bloodstream. With more blood in the stream, the amount of cholesterol per deciliter declines, producing a lower total cholesterol reading. A second possibility is that people tend to eat less and be more active in summer. They lose weight, and weight loss equals lower cholesterol.

The first bit of wisdom from this study is obvious: Being physically active reduces your cholesterol level. The second is that environment matters. In other words, if you're planning to start a new cholesterol-buster diet, you may just do better to start during the cool weather, when your efforts may lower your total cholesterol as much as 12 points over a reasonable period of time, say, six months. Then when your doctor runs a follow-up test the following summer, you'll get the added benefit of the seasonal slip to make you feel really, really good about how well you're doing. And there's this: For more on controlling your cholesterol, zip out and get yourself a copy of (what else?) Controlling Cholesterol For Dummies. By me.

Living with lipoproteins

A lipoprotein is a fat (lipo = fat, remember?) and protein particle that carries cholesterol through your blood. Your body makes four types of lipoproteins: chylomicrons, very low-density lipoproteins (VLDLs), low-density lipoproteins (LDLs), and high-density lipoproteins (HDLs). As a general rule, LDLs take cholesterol into blood vessels; HDLs carry it out of the body.

A lipoprotein is born as a chylomicron, made in your intestinal cells from protein and triglycerides (fats). After 12 hours of traveling through your blood and around your body, a chylomicron has lost virtually all of its fats. By the time the chylomicron makes its way to your liver, the only thing left is protein.

The liver, a veritable fat and cholesterol factory, collects fatty acid fragments from your blood and uses them to make cholesterol and new fatty acids. Time out! How much cholesterol you get from food may affect your liver's daily output: Eat more cholesterol, and your liver may make less. If you eat less cholesterol, your liver may make more. And so it goes.

Churning out harmful lipoproteins

Okay, after your liver has made cholesterol and fatty acids, it packages them with protein as very low-density lipoproteins (VLDLs), which have more protein and are denser than their precursors, the chylomicrons. As VLDLs travel through your bloodstream, they lose triglycerides, pick up cholesterol, and turn into low-density lipoproteins (LDLs). LDLs supply cholesterol to your body cells, which use it to make new cell membranes and manufacture sterol compounds such as hormones. That's the good news.

The bad news is that both VLDLs and LDLs are soft and squishy enough to pass through blood vessel walls. The larger and squishier they are, the more likely they are to slide into your arteries, which means that VLDLs are more hazardous to your health than plain old LDLs. These fluffy, fatty lipoproteins carry cholesterol into blood vessels, where it can cling to the inside wall, forming deposits, or plaques. These plaques may eventually block an artery, prevent blood from flowing through, and trigger a heart attack or stroke. Whew! Got all that?

VLDLs and LDLs are sometimes called "bad cholesterol," but this characterization is a misnomer. They aren't cholesterol; they're just the rafts on which cholesterol sails into your arteries. Traveling through the body, LDLs continue to lose cholesterol. In the end, they lose so much fat that they become mostly protein — turning them into high-density lipoproteins, the particles sometimes called "good cholesterol." Once again, this label is inaccurate. HDLs aren't cholesterol: They're simply protein and fat particles too dense and compact to pass through blood vessel walls, so they carry cholesterol out of the body rather than into arteries.

That's why a high level of HDLs may reduce your risk of heart attack regardless of your total cholesterol levels. Conversely, a high level of LDLs may raise your risk of heart attack, even if your overall cholesterol level is low. Hey, on second thought, maybe that does qualify them as "good" and "bad" cholesterol.

Setting limits on the bad guys

At one point, back in the dawn of the Cholesterol Age, like, say, five years ago, the "safe" upper limit for LDLs was assumed to be around 160 mg/dl. Now, the National Heart, Lung, and Blood Institute, American College of Cardiology, and the American Heart Association have all put their stamps of approval on the National Cholesterol Education Program's (NCEP) recommendations for new, lower levels of LDLs based on the presence of the risk factors I list under "Cholesterol and heart disease." You know — diabetes, high blood pressure, obesity . . . those risk factors.

For healthy people with two or more risk factors, the new goal is to push LDLs below 130 mg/dl. For high-risk patients with heart disease or blood vessel problems and more than two risk factors, it's LDLs below 100 mg/dl. For very high-risk patients who are hospitalized with heart disease or have heart disease plus several risk factors, LDLs should be under 70 mg/dl. If necessary, the NCEP suggests using cholesterol-busting "statin" drugs such as atorvastatin (Lipitor).

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