December 13, 2011


What is cholesterol?

Read Time 3 minutes

I know much more about cholesterol today than I did even two years ago, let alone when I was mindlessly reiterating “standard” cholesterol recommendations to patients years ago.

You can’t talk about nutrition without mentioning cholesterol, but most folks (including many of the doctors who tell you yours may be too high) don’t know what cholesterol actually is, let alone the actual risk it portends.  I’m going to be doing a lot of writing about the confusion over cholesterol in the future, but I want to very quickly give you a few things to consider.

    1. Cholesterol is a “waxy” substance generally produced by our liver.  Without we could not live, which is to say cholesterol is vital for many functions in our body.
    2. There are many types of cholesterol particles that vary by size, density, and function
    3. More often, what people mean when they say “cholesterol” is “lipoprotein,” and these are not the same thing. I’ve tried resisting the urge to include this figure, but I just can’t help it.  Below is a figure of a lipoprotein particle.  Hopefully you can make out that cholesterol is a part of the lipoprotein, along with other molecules like triglycerides (TG), cholesterol esters (CE), phospholipids, and apoproteins.
By AntiSense (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons
  1. As you’ve probably heard, there low density lipoproteins (LDL), high density lipoproteins (HDL), and a few variants in between of intermediate and very-low density, respectively (i.e., IDL, VLDL).
  2. Historically, we’ve been taught that LDL is “bad,” while HDL is “good.”  This is true in the same way it’s true to say rugby is safer than football, because they don’t wear helmets and don’t hit quite as hard.  It sort of misses the important nuances (which I won’t go into here).  Unfortunately, it’s far too simple to assert that LDL is “bad,” though it is easier to say HDL is “good.”
  3. The aspect of LDL that makes it “bad” is not the cholesterol concentration (the so-called LDL-C, which is what your doctor measures when you get a cholesterol test), it’s probably the actual particle itself (the so-called LDL-P, which you never get checked unless you have a fancy test called a lipid nuclear magnetic resonance – or NMR for short – test).  If that doesn’t confuse you enough, this might: there are different types of LDL molecules, which vary in size.
  4. As a general rule, ceteris paribus, the smaller the LDL particle, the more damage it causes.  This is actually a bit controversial.  There are some (pretty smart folks) who make the case that a particle of LDL is a particle of LDL – it’s only the number of them that matter, not the size.  In other words, the only thing about LDL particles that matter is their number, not their size or the concentration of cholesterol within them.
  5. Confusing this even more, in about a third of folks, LDL-C (the concentration of LDL cholesterol) and LDL-P (the number of LDL particles) are actually what call discordant (i.e., not predictive of the same thing)
  6. Our entire belief that high LDL-C is “bad” stems from the following logic: taking a type of drug called a statin lowers LDL-C and lowers risk of heart disease, ergo high LDL-C must be “bad.”  The problem with this logic, I hope you can see, is that it negates the fact that the benefit of statins could result from doing something other than lowering LDL-C.  I personally am not convinced that statins exert their protective benefits by reducing high LDL-C.  I believe they reduce, specifically, the number of small particles and overall inflammation, and that these effects are likely what confer their benefit.  More about this later.
  7. While HDL is considered “protective,” it’s not uniformly true.  There are actually many different HDL particles (of course, the standard test only measuring the concentration of cholesterol in HDL, denoted HDL-C).  If that weren’t bad enough, different technologies (e.g., VAP versus NMR) actually use different nomenclature to describe the different subparticles of HDL.  As a general rule, the larger the HDL particle, the more mature it is, the more protective it is.  HDL particles are probably protective for two reasons: 1) they can enter and exit the artery wall without causing damage, unlike the LDL particle, and 2)  they can carry damaging particles called oxysterols from the artery wall back to the liver via process called “reverse cholesterol transport” or RCT.
  8. Triglyceride (TG) levels in the blood are better when “low” than when “high.” Of course the cutoff that constitutes “high” is debated.  Standard tests suggest an upper limit of 150.  The real whizzes on the topic actually suggest TG levels should be below 80.  In fact, combining HDL-C and TG into a ratio (i.e., TG/HDL-C) is probably the single best predictor of cardiac risk you can derive from a standard cholesterol test.  The lower the ratio, the lower your chances of having an “adverse cardiac event,” as the medical community describes it (e.g., a heart attack).

…and that was short version of Cholesterol 101.

Photo by Emily Morter on Unsplash

Disclaimer: This blog is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this blog or materials linked from this blog is at the user's own risk. The content of this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard, or delay in obtaining, medical advice for any medical condition they may have, and should seek the assistance of their health care professionals for any such conditions.


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