Heart disease handbook--part 2: Deciphering blood cholesterol

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Look around you. Count off every fifth adult you see--nearly 38 million Americans in all--and you have the number of people with high blood cholesterol. All are at risk for athero-sclerosis, the type of heart disease that clogs arteries and can eventually stop blood flow to the heart. The sometimes deadly consequences? A heart attack.

Despite the danger of elevated blood cholesterol to an otherwise healthy heart, cholesterol itself is not the enemy. Your body needs cholesterol to build healthy cell membranes and to manufacture hormones and bile acids. The problem is not cholesterol per se, but too much of it. To be accurate, it's too much of the wrong kind that gets you into trouble.

A Little About Lipoproteins. Your risk of heart disease is determined by the transportation system that ferries cholesterol through the body. Just as oil and water do not mix, fat-soluble cholesterol does not mix well with blood. So it relies on carriers called lipoproteins, made up of fat (i.e. lipid) that's bundled together with protein, enabling it to escort cholesterol through the bloodstream.

Low-density lipoproteins (LDL's) carry cholesterol to artery walls, dumping their cholesterol load there, where it congregates to form artery-clogging plaque that can lead to a heart attack or stroke. Such single-minded evil intent has earned LDL's the nickname "bad cholesterol." About two-thirds of the cholesterol in your blood is transported as LDL's.

High-density lipoproteins (HDL's) carry cholesterol away from arteries, scooping it up from artery walls and taking it to the liver for disposal. Such a life-saving role has rightfully earned it the tag "good cholesterol."

To keep the confusing terms straight, remember: You want your low-density lipoprotein level to be low, and your high-density lipoprotein level to be high.

Time-Honored Testing for Cholesterol. Adults should get their cholesterol checked every five years, more often if numbers are above the desirable range (see chart) or if there are other risk factors (see Part 1, February 1997).

Besides measuring for total blood cholesterol, it's best to get a separate measure of HDL's. High HDL's temper the risk of a total cholesterol that's above "desirable." Low HDL's, on the other hand, signal heart attack risk even if total cholesterol is well within the desirable range.

If your total cholesterol is high or borderline-high or your HDL's are low, you'll need to check your LDL level. Unlike total cholesterol, LDL's should be measured after a nine- to 12-hour fast. It's still fairly standard practice for labs to indirectly calculate LDL levels from blood levels of triglycerides--the form of fat circulating in your body. But since triglycerides can be affected by a recent meal, you must fast before LDL testing. It's considered acceptable to measure HDL's without fasting, though a recent government panel of experts recommended fasting even for HDL's.

You can get a complete lipid profile --total cholesterol, HDL's, LDL's, and triglycerides--for about $30 to $50. Home cholesterol tests are less costly ($10 to $20), but measure only total cholesterol and are not easy to perform, since you must prick yourself and collect the blood properly.

Connecting the Numbers. To get a better sense of your heart disease risk, you should understand what your blood lipid levels mean and how these numbers relate to one other.

"If LDL's are high, it's a problem, but if, [in addition], HDL's are low, your risk is even higher," says Josef Coresh, M.D., Ph.D., of The Johns Hopkins Medical Institutions in Baltimore.

Also, check your total-cholesterol-to-HDL ratio. Although experts hesitate to pin down an "ideal" ratio, most consider a total-to-HDL ratio of 5:1 (reported as 5) or higher to be risky. (To calculate your ratio, divide total cholesterol by HDL's--e.g. 200 / 50 = 4.)

How Bad is Bad? "'Bad' cholesterol is a relative term," explains Coresh. "All LDL's are probably bad, but small, dense LDL's are worse." Worse, that is, than large, buoyant LDL's.

Recent studies suggest that people with a predominance of small, dense LDL's have a greater risk of heart disease than those with larger LDL's. That's the case for about one in three men and one in six postmenopausal women. What's more, small LDL's are linked to other risk factors, like high triglycerides and low HDL's.

Why is small badder than bad? Small LDL's are more easily oxidized than large LDL's. Research has shown that LDL's wreak the most havoc on arteries only after they've been oxidized, that is chemically changed by oxygen, which unleashes destructive molecules called free radicals.

If that's the case, researchers have reasoned, then perhaps antioxidants can block LDL's from being oxidized, thus heading off the clogging of arteries. Vitamin C and beta-carotene have not shown much promise, but vitamin E has.

The size of LDL's is influenced, in part, by your genes, according to Ronald Krauss, M.D., of Lawrence Berkeley National Laboratory in Berkeley, California. However, LDL size might be increased by weight loss, exercise, a low-fat diet, and to a lesser extent, prescription doses of niacin. LDL size is not something routinely measured. A recent study found it doesn't predict risk any better than a full lipid profile.

A Diet-Drug Partnership. Battling blood cholesterol down to desirable levels is a key step in preventing heart disease or its recurrence. That was demonstrated dramatically in research just published in January. Of more than 1,300 people who had undergone coronary bypass surgery and were following heart-healthy diets, those who were also treated with drugs that aggressively lowered LDL's (to below 100) were able to reduce the progression of atherosclerosis 31% more than those treated with drugs that moderately lowered their LDL's (to 130).

But the first step to keeping blood cholesterol in check is to improve your diet. That means cutting back on fat (especially saturated fats and trans fats), keeping dietary cholesterol within reason, and eating more fruits, vegetables and foods rich in soluble fiber like oats and dried beans. (See part 4 of series.) Losing weight, if necessary, is also part of the equation.

If that's not enough to bring your numbers into desirable range, your doctor may prescribe drugs. There's no question that new cholesterol-lowering drugs called "statins" or the often-overlooked B vitamin niacin can substantially reduce heart disease risk. These drugs are not without possible side effects, however. And taking drugs does not negate the importance of a heart-healthy diet. Without it, medication is not as effective.

Whether you want to prevent heart disease or keep an existing condition from getting worse, you need to take steps now to control your blood cholesterol: Eat healthfully, exercise, maintain a healthy weight and don't smoke.

Next month: A new look at the risk of high blood triglycerides.

What Those Numbers Mean

Total Cholesterol
Less than 200 Desirable
200-239 Borderline-High Risk
240 or more High Risk

HDL ("Good") Cholesterol
60 or more More Desirable (protective)
35-59 Desirable
Less than 35 High Risk

LDL ("Bad") Cholesterol
Less than 100 Desirable (with heart disease)
Less than 130 Desirable (if no heart disease)
130-159 Borderline-High Risk
160 or more High Risk

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By Adrienne Forman, M.S., R.D.

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