LDL is Not Always the Bad Cholesterol

LDL cholesterol is often described as “bad,” but the fact is that it is essential to human life. It’s actually possible to have too little LDL cholesterol, so little cholesterol that the immune system cannot protect the body against infectious diseases and cancer.

Most of the cholesterol in the human body is made by the body itself, not extracted from food. Every cell in the human body can make at least part of the cholesterol it needs from triglycerides, which are the storage form for unused fatty acids and sugar. Every cell in the human body has to have cholesterol to make its outer membrane, which keeps the contents inside the cell from being dissolved by the bloodstream.

Cholesterol also has to protected against dissolving in the bloodstream. Every piece of cholesterol is protected by a lipoprotein, a kind of protein that surrounds the waxy, fatty cholesterol inside. The lipoprotein itself is soluble in water.
What is LDL? Cholesterol begins its travels around the body as VLDL, or very low-density lipoprotein. These are large pieces of cholesterol that are used for repair and fuel. Cells take the cholesterol they need from the particle of VLDL, eventually shrinking it down to LDL, or low-density liproprotein.

LDL is important to the immune system. Larger pieces of LDL help the immune system conduct signals. Slightly smaller pieces of LDL serve as food for macrophages, literally “big eaters,” large white blood cells that can literally surround a bacterium and consume it. When macrophages aren’t dining on bacteria, they are dining on LDL.

So, what’s not to like about fuel for your immune system? Here are the three things everyone needs to know about LDL.

  1. Whether or not LDL has the potential to cause heart disease depends on the kind of lipoprotein to which it is attached. Bigger pieces of LDL are attached to a protein called apo-A. They are too big to be eaten by macrophages. Smaller pieces of LDL are attached to a protein called apo-B. They are just the right size to be eaten by macrophages. Hardening of the arteries isn’t caused by cholesterol, it’s caused by macrophages that get stuck in the lining of the arteries when they try to consume the smaller bits of LDL cholesterol. This process that actually creates “bad” cholesterol.
  2. Your total LDL number offers only a rough estimate of your risk of heart disease. The best number for predicting risk of heart disease is not LDL, or the ratio of LDL to HDL, but rather the ratio of apo-B to apo-A (or, more specifically, in terms of the names scientists and medical labs use to identify these lipoproteins, apoB100 and apoA1). You can have high LDL and and low apo-B, and not really be at increased risk for heart disease. You can have low LDL and high apo-B, and actually need a cholesterol-lowering drug. Total LDL cholesterol numbers don’t give you or your doctor the information needed.
  3. Your doctor needs to measure apo-A and apo-B at least at the beginning of your treatment. Then it is possible to use the LDL and HDL numbers your doctor probably usually takes to monitor your progress.

Scientists have known the truth about LDL cholesterol for nearly 30 years, but they are understandably hesitant to admit the system everyone uses is wrong. The cost of apo-B/apo-A testing has fallen to about US $50, however, so you should avail yourself of the possibilities of being sure you are really getting the treatment you need to have truly healthy cholesterol numbers.