Cholesterol Basics

All too often, someone will tell me “my cholesterol is usually around 200” or “I think my cholesterol was normal”, without knowing much more information. This is unfortunate, because your cholesterol profile is one of the biggest determinants of your risk of a heart attack or stroke. It is dependent on your genetics, your diet, and your activity level. Your cholesterol profile, in a very literal sense, is a reflection of who you are.

“Your cholesterol profile is a reflection of who you are.”

– Doctor T

There are three components to a basic cholesterol profile, with two bad parts and one good part. When added up with a certain formula, these components give us the total cholesterol value. As a result, the total cholesterol number is useless on its own, without knowing how much is good and how much is bad. If you already know the basics, jump ahead to our article on the most recent cholesterol management guidelines.

People often worry about having a bad cholesterol number. In medicine, we often say “treat the patient, not the number.” What this means is that any cholesterol value should be analyzed in the context of the lipid profile as a whole and other risk factors as well. Any “bad” value should be interpreted as increasing risk, and will often be addressed in a similar way (usually lifestyle modifications, and possibly medication) regardless of the specific abnormality. Before we get further into that, though, let’s review the components of the lipid profile.

“Treat the patient, not the number.”

– Doctor T

LDL cholesterol

This is the bad cholesterol (remember “L” for “lousy”). A wealth of data suggests that LDL cholesterol is a significant driver of atherosclerotic disease that leads to heart attacks and strokes, and that decreasing LDL via lifestyle changes and medications decreases that risk. This is what is referred to as “the LDL hypothesis”.

An ideal LDL level is <100 mg/dL (although <70 may be optimal in very high risk patients).

As various internet sites are quick to point out, the LDL hypothesis is not bulletproof, and there is some data that contradicts it. What remains, however, is an overwhelming amount of data that statin medications (which decrease LDL) reduce the risk of cardiac events and death in a broad range of populations – and this has been established in dozens of large, high quality randomized, controlled trials – the gold standard for proving causation in medicine.

HDL cholesterol

This is the good cholesterol (remember “H” for “happy”). Higher HDL levels are associated with a lower risk of cardiovascular risk. We often think of HDL as a “reverse transport” molecule that picks up cholesterol from the arteries and carries it back to the liver for processing. However, it is not entirely clear that high HDL prevents atherosclerosis or that low HDL causes it. Regardless, low HDL levels are associated with increased cardiac risk, and that can not be ignored. A level less than 40-50 mg/dL is considered low.

Triglycerides

Along with LDL, triglycerides are an atherogenic form of lipid, meaning that they are bad. They contribute to the development of atherosclerotic disease and high levels increase the risk of heart attacks and strokes. Extremely high triglycerides levels can cause a dangerous condition called pancreatitis. An ideal triglyceride level is < 150 mg/dL, while >500 is considered very high.

Total Cholesterol

Why don’t the above three values add up to total cholesterol? Because triglycerides are not cholesterol. They are associated with cholesterol in particles called VLDL in a 5:1 ratio, so VLDL cholesterol is estimated by dividing the triglyceride value by 5.

Remember pre-algebra class? In a standard lipid profile, the LDL is calculated using the following formula:

Total cholesterol = LDL + VLDL + HDL

Substitute VLDL for triglycerides/5 and rearrange and you get:

LDL = Total cholesterol – HDL – triglycerides/5

This formula is not always accurate, especially if triglycerides are high, but LDL can be measured directly if necessary.

Non-HDL cholesterol

By rearranging the above equation, the non-HDL cholesterol basically comes out to LDL + triglycerides/5. This is an important number because it combines the two bad forms of cholesterol, and it is more strongly associated with risk than the LDL value alone. It is also more accurate than a calculated LDL when triglyerides are high, and it can be interpreted more easily on a non-fasting specimen.

How do I interpret these numbers and treat them?

People often ask how to treat a particular abnormal cholesterol value, but the important thing is to assess the risk associated with these abnormalities, and decrease overall risk. This usually involves a certain set of recommendations regardless of the specific abnormality. Know your lipid profile, and discuss it with your doctor, but this algorithm is a good place to start:

1. Very high triglycerides (>500 mg/dL) – see below
2. Assess cardiovascular risk
3. Lifestyle modifications
   • Heart-healthy diet
   • Increase exercise
   • Stop smoking
4. With the help of your physician:
   • Control blood pressure
   • Control blood sugars
   • Stop smoking
   • Consider aspirin and/or statin based on guidelines
5. Refer below for specific patterns

High LDL

In addition to the above steps, the main thing to do to target a high LDL level is to modify fat intake.

Everyone should avoid trans fats, which raise LDL cholesterol without any beneficial effect on HDL. Fortunately, trans fats are currently being phased out of the US food supply, due to increased awareness of their dangers as well as government regulation.

Saturated fats are a kind of fat that are found largely in animal products. Red meat, the skin in the chicken, and dairy (especially products such as butter, ice cream, and cheese) are high in saturated fat. Saturated fats increase both LDL cholesterol and HDL cholesterol, so these effects theoretically would offset each other in terms of cardiac risk. Replacing saturated fats with carbohydrates appears to be bad for health, but replacing them with unsaturated fats is recommended by the American Heart Association to improve heart health. This is because unsaturated fats tend to increase HDL cholesterol without affecting LDL cholesterol. Many believe that the shift from lard and butter to vegetable oils over the years has already had a dramatic impact on public health.

Additional measures for a high LDL include plant stanols (found in products like Benecol) and soluble fiber such as those found in oatmeal and psyllium (found in products like Metamucil). We will devote a future post to dietary treatment of LDL.

Because statin medications primarily target LDL and result in a profound reduction in this number, they are the mainstay of therapy for very high LDL levels, and also for less elevated levels that add to cardiovascular risk from other causes. Statin therapy is a key focus of the new cholesterol treatment guidelines.

Low HDL

Low HDL is a marker for increased cardiovascular risk. Unfortunately, it is very difficult to increase HDL. The above lifestyle modifications can have a modest effect on increasing HDL. Medications that raise HDL have not convincingly demonstrated a decrease in cardiac events.

Alcohol consumption is known to increase HDL, and in the past was thought to result in decreased coronary disease and death, but two recent studies have cast doubt on these findings. Stay tuned for a future blog post discussing alcohol and heart disease.

Very high triglycerides

Triglyceride levels greater than 500 mg/dL can cause a dangerous condition called acute pancreatitis, and the risk increases as the triglyceride level increases. Levels this high should be discussed promptly with a physician.

In this range, triglyceride levels are driven largely by dietary fat, so a very low fat diet should be instituted, with less than 25 to 40 grams of fat consumed per day. In this case, even “healthy” unsaturated fats should be restricted, as they will increase triglyceride levels.

Moderately elevated triglycerides

Triglyceride levels greater than 150 mg/dL but less than 500 mg/dL increase cardiovascular risk. In this range, triglycerides are driven largely be carbohydrate consumption. The recommended dietary modifications are similar to a standard “heart-healthy diet” including:

• total calorie consumption that maintains weight or leads to weight loss if overweight
• avoidance of sugars
• carbohydrate reduction

Low HDL + high triglycerides

These 2 factors are often associated with abdominal obesity, elevated blood pressures, and prediabetes or diabetes. Combinations of these risk factors are often termed the “metabolic syndrome.” Read our post on prediabetes to learn why this is so important and what you can do about it.

Summary

Evaluating an abnormal (or even normal) lipid panel should be done in the context of the person as a whole. This includes an assessment of cardiac risk, and interventions to reduce that risk. Sometimes these interventions are targeted specifically at the lipid abnormality, but often they relate to other risk factors or health in general.