There are few things in modern medicine clearer than the link between cholesterol and heart disease. Over the last decade, research studies involving thousands of patients with heart disease have shown that lowering cholesterol decreases your risk of having a heart attack by as much as 40 percent.

Cholesterol is a substance your body actually needs. It’s important in the production of certain hormones, including estrogen and testosterone, and it helps maintain the integrity of the walls of all the cells in your body. Cholesterol is produced in the liver from the foods we eat—mainly fats, but also proteins and carbohydrates.

It can also come directly from foods containing cholesterol. But even though it is an essential substance, as many as 100 million Americans—nearly half of all adults—may have too much of it in their bloodstream. Even so, one-third of people with high cholesterol have no idea they have it.

Of those who do know, only one-third are being treated for their high cholesterol, and fewer than half of people receiving treatment have been treated enough to bring their cholesterol levels into safe range. Excess cholesterol collects on the insides of the artery walls in fatty streaks.

It’s one of the primary constituents of the plaques that cause arteries to narrow and “harden,” making them vulnerable both to rupture and blockage. As we’ve seen, when this occurs in arteries supplying the heart, it can damage the heart. We normally think of this process as occurring in older adults, but in fact it begins at an early age.

Autopsies of American soldiers killed in the Korean War first alerted doctors to the fact that even healthy young men already have some fatty streaks, or atherosclerotic plaque buildup in their blood vessels. We now know that many people have fatty streaks by age twenty—or even earlier.

As with high blood pressure, high cholesterol has no obvious symptoms; most of the people who have cholesterol levels that are too high don’t even know it. The good news is that—again, like high blood pressure—high cholesterol can be diagnosed and treated. Yet as many as two-thirds of the people with high cholesterol go untreated.

Cholesterol Tests

The only way to find out if your cholesterol levels are too high is to have a blood test called a “lipid panel.” This test typically measures four things:

• LDL (Low-Density Lipoprotein) Cholesterol Cholesterol is composed of proteins and fats. LDL cholesterol has a low density, or low concentration, of protein but a high density of the fats that cause atherosclerosis. It’s also known as “bad” cholesterol.

• HDL (High-Desity Lipoprotein) Cholesterol HDL cholesterol has a high density of protein and relatively little fat. It collects excess fat in your bloodstream and carries it to the liver for disposal. It’s a sort of fat scavenger. That’s why it’s known as “good” cholesterol. If your HDL is low, those excess fats build up instead of being removed.

• Total Cholesterol This is a total measure of the cholesterol in your blood and includes LDL and HDL cholesterol as well as some other cholesterol components.

• Triglycerides These are another form of fat the body makes from sugar, alcohol, or extra calories.

All four of these measurements provide useful information, but by far the most important for people with heart disease is LDL cholesterol, because that’s the one most closely linked to atherosclerosis and the one that can be most easily treated.

Based on strong evidence from many clinical studies, heart experts have developed targets for your cholesterol levels (usually reported in milligrams per deciliter, or mg/dL):

• LDL cholesterol should be under 100 mg/dL for patients with heart disease (or 70 mg/dL for very high risk patients)
• HDL cholesterol should be 40 mg/dL or higher
• Total cholesterol should be below 200 mg/dL
• Triglycerides should be below 150 mg/dL

Recent clinical trials have caused the National Cholesterol Education Program, the authoritative group of experts that is convened by the National Heart, Lung, and Blood Institute of the National Institutes of Health, to revise their recommendation for the target level of LDL cholesterol.

The goal for people with heart disease remains less than 100 mg/dL, but now they also endorse a target of less than 70 mg/dL for high-risk patients, which includes patients with established heart disease. The new target is called an option, or a “reasonable clinical strategy.”

The revised recommendations say that an LDL of less than 70 mg/dL is a reasonable clinical strategy on the basis of available clinical evidence, and an LDL of less than 100 mg/dL remains the strong recommendation. The guidelines indicate that the lower target is particularly favored for patients with established heart disease and either:

1. Other major risk factors (such as diabetes)
2. Severe and poorly controlled risk factors (including continued smoking)
3. High triglycerides (200 mg/dL or greater) and non-HDL cholesterol of 130 mg/dL or greater with an HDL of 40 mg/dL or lower
4. Hospitalization for a heart attack.

The reason that they are not stronger in recommending the level of less than 70 mg/dL is that several studies are in progress to evaluate reducing the LDL to very low levels. The principal reason for the recommendation change is the Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) trial, which found that patients benefit from lowering cholesterol levels below the old target.

Over 4,000 patients who were hospitalized with heart disease were randomized to a high dose (80 mg) of atorvastatin or a standard dose (40 mg) of pravastatin. With the high dose of atorvastatin, the LDL was lowered to around 62 mg/dL, whereas the standard dose of pravastatin lowered the LDL to about 95 mg/dL.

The more aggressive approach was associated with a 16 percent reduction over two years in the risk of cardiovascular events. The advantage of the more aggressive strategy is what led to this change in the recommendation.

Lifestyle Changes

If your LDL cholesterol is between 100 and 130, the current guidelines say that you should aim to lower it through lifestyle changes— that is, through diet, exercise, and weight management—before moving to medications. As with blood pressure control, the first step has to do with lifestyle.

Diet

Scientists believe that the amount of fat you eat is directly related to how high your LDL cholesterol level is. But there are many different kinds of fats. Understanding the differences between types of fats is so important to preventing and controlling heart disease.

In general, however, the American Heart Association (AHA) guidelines suggest that you limit your overall fat intake to less than 30 percent of your total daily calories. Of that total 30 percent, saturated fats should represent less than 7 percent. Cutting fat works: researchers have shown that a low-fat diet can lower LDL cholesterol levels by 7 to 9 percent in people with high cholesterol.

The AHA experts also recommend increasing your consumption of vegetables that contain LDL cholesterol–lowering monounsaturated fatty acids and fiber. Fatty acids are labeled based on their chemical structure. Monounsaturated fatty acids are a major nutrient in the food supply of the Mediterranean countries.

Olive oil and canola oil are examples of high monounsaturated fatty acid foods. Current evidence also suggests that eating more foods that contain omega-3 fatty acids, found in many kinds of fish, also can protect you from heart problems. Salmon is an example of a high omega-3 fatty acid food.

Exercise

Physical activity increases HDL cholesterol and lowers LDL cholesterol. Indeed, one recent study showed that increased exercise alone can significantly improve your cholesterol profile.

The recommended goal for exercise is moderately intense physical activity (the equivalent of briskly walking at three to four miles per hour for most healthy adults) for thirty minutes per day, at least five times per week. Of course, how much you can exercise depends on your overall health, so talk to your doctor about a program that’s best for you.

Weight Management

If you are overweight—and many Americans are—losing even a few pounds will lower your LDL cholesterol. This is true regardless of what you eat, but a calorie-controlled diet that is low in saturated fats and cholesterol is best; it will help all other efforts to lower your LDL cholesterol and help keep it low over time.