Confounded by Cholesterol?

Cholesterol has been and continues to be a confusing topic for many people, especially in light of recent hype about high-fat, low-carbohydrate diets. Here are some of the many questions readers have had about cholesterol.

* I know avocados are high in fat, but how much cholesterol do they have?

There is no cholesterol in avocados; cholesterol is only found in animal products. Avocados are quite high in fat, but it is mostly the unsaturated type. That makes it a pretty good fat as fats go, but avocados are sometimes banned from a cholesterol-reducing diet because they contribute greatly to overall fat intake, which may in turn raise serum cholesterol.

* If I boil meat before eating it, will that get rid of the cholesterol? What if I trim off the visible fat?

Either of these methods will get rid of some of the fat, but cholesterol (which is a fat-like substance) is also present in the lean tissue of meat. In fact, there is as much cholesterol in lean meat as there is in meat fat. Three ounces of untrimmed fatty beef has about 82 milligrams of cholesterol, and lean beef, with most of the fat trimmed or boiled away, has about 79. So the difference is insignificant.

The one thing that boiling your meat might do is render it completely inedible, thereby forcing you to eat more vegetables and low-fat alternatives.

* Which foods contain good cholesterol and which contain bad cholesterol?

The cholesterol in foods is all the same. It doesn’t become good or bad until it is processed by the body. The fats and cholesterol you eat, along with the cholesterol produced by your body (mostly in the liver), are carried through the body by structures known as lipoproteins. These packages are combinations of fats, proteins and cholesterol.

The so-called bad cholesterol package (low-density lipoproteins, or LDL) is high in cholesterol, which it carries through the bloodstream to be used by the body to build cells and hormones, insulate nerves, and so forth. What isn’t needed tends to be deposited in the artery walls, and that’s when all the trouble begins.

The good cholesterol (high-density lipoproteins, or HDL), on the other hand, is a similar package but with a different composition. As it circulates through the system, it picks up some of the extra cholesterol lying around in the arteries and takes it back to the liver to be reprocessed. That’s why the more HDL you have, the better off you are. LDL can be reduced by dietary changes, and HDL can be increased by exercise and diet.

* What is a safe cholesterol level?

To some extent this depends on your age and sex, but the National Heart, Lung and Blood Institute recommends that people younger than 30 have cholesterol levels of 180 or less; for the rest of us, the level should be 200 or less. These are lower levels than formerly acceptable, so if you haven’t had your cholesterol tested for a while, it might be a good idea to do so.

When you get the results, look at the individual levels of HDL and LDL. A low LDL (under 130) or a high HDL (over 35) are now considered protective. In addition, a high LDL is thought to be an independent risk factor for heart disease. The test should be done after an overnight fast.

* What kinds of foods are especially low in cholesterol?

As we have said before, only animal products contain cholesterol. That means that all fruits and vegetables are good, as are whole grains, nuts, soybeans, lentils and the like. Animal products among the lowest include skim milk, cottage cheese, and low-fat or nonfat yogurt. Among the worst offenders are liver, eggs and fatty meat.

No matter what you eat, you should limit your cholesterol intake to no more than 250 to 300 milligrams per day.

* If I eat eggs and oatmeal in the same meal, will the oat bran cancel out the cholesterol in the eggs?

No. Although oat bran is known to lower blood cholesterol levels, along with many other foods high in soluble fiber, it must be used along with an overall reduction in fat and cholesterol intake. Unfortunately, there is nothing magic about oat bran that you wouldn’t find in other foods containing water-soluble fiber like beans, peas, carrots, corn and some fruits like prunes.

* Because there seem to be good drugs on the market to control cholesterol, why not just eat whatever we want and take the drugs?

That seems like a good idea in theory, but the U.S. Food and Drug Administration recommends that these drugs only be used when a combination of diet and exercise fails. The drugs are intended for people with genetic disorders or metabolic diseases that raise cholesterol to dangerous levels. And, of course, a healthy diet instead of pills provides much more than just protection against heart disease.

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Dr. Sheldon Margen is professor of public health at UC Berkeley; Dale A. Ogar is managing editor of the UC Berkeley Wellness Letter. They are the authors of several books, including “The Wellness Encyclopedia of Food and Nutrition.” Their column runs every Monday. Send questions to Dale Ogar, School of Public Health, UC Berkeley, CA 94720-7360, or daogar@uclink4.berkeley.edu.