Lesson #1: Cholesterol


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Cholesterol

Eating cholesterol does not cause “high cholesterol”, eating fat does not make you fat.  In fact, both of these dietary substances are vital for a healthy body.

What is cholesterol??

First of all, for illustrative purposes, I am going to talk about “blood cholesterol” as a different substance than “cholesterol” because what we talk about as “blood cholesterol” is not cholesterol per se, but rather the carriers of cholesterol.  Most people are probably familiar with hearing cholesterol talked about as something in blood.  Your level of blood cholesterol is determined from your blood test and is divided into VLDL, LDL, HDL and Triglycerides.  Lowering blood cholesterol is what people take medication (statins) for.

The cholesterol used in your body is made by your body.  The cholesterol you eat, like in egg yolks, shrimp and lobster, does not go directly into the blood stream, it gets digested/broken down.  In fact, eating a moderate amount of cholesterol does not have any effect on your level of blood cholesterol.  (2 egg yolks per day is considered a moderate amount.)

Cholesterol is used everywhere in the body, and it is actually vital to cell membranes and plays other important roles in human metabolism.  Cholesterol is needed for use in repair of cell membranes and synthesis of steroid hormones and bile salts.  Cholesterol is so important to our bodily functions that the human body synthesizes cholesterol in many body tissues, mostly the liver, but also adrenal cortex, skin, intestines, testes and ovaries.

Blood Cholesterol

The blood cholesterol numbers that we get in a blood test are actually not counting cholesterol per say, but are the levels/amounts of the carriers of cholesterol.

Because of this, I think of “blood cholesterol” as little cholesterol boats: boats to carry cholesterol through the bloodstream.  Our blood is water-based, and cholesterol is oil based, and we all know that oil and water don’t mix, so in order for cholesterol to get to our cells, where it is needed, they need special carriers to carry them through our largely water-based bodies.

Blood cholesterol starts its journey in the liver.  The liver creates cholesterol, lipids, and Very Low Density Lipoproteins (VLDLs) (lipoproteins are complexes of protein and fat).  These VLDLs are part of the “blood cholesterol”, the cholesterol boats.  The “boats” get filled with cholesterol and lipids, and then launched into the bloodstream.

(Lipids are similar to amino acids in that they are like building blocks – many substances, like hormones, are built with lipids.  Lipids are NOT created only when we eat fat or cholesterol – lipids are formed also as a by-product of carbohydrate and protein digestion.)

The first stop for the VLDLs is fat cells and muscle cells, where the VLDL unloads some of its lipid cargo.  Lipids get stored in fat cells, or sent to muscles for energy production.  Once the VLDL unloads some of its lipid cargo, it increases in density a little bit and is then called Low Density Lipoprotein (LDL).

Out of all of the blood cholesterol parts (VLDL, LDL, HDL), LDLs are the most plentiful.  Their role is important: they deliver cholesterol to cells.  The LDL comes up to a cell and knocks on the “blood cholesterol door” of the cell.  LDLs (including their cholesterol and lipid cargo) are invited into the cells and are used for cell repair and energy production.  When the LDL need is met, the cell takes away the “blood cholesterol doors”.

Note: If you remember, in a previous lesson I introduced the idea that every cell in your body has a bunch of different special doors.  These doors are very picky and finicky.  They are designed to let in specific molecules.

High Cholesterol

The problem comes when there are too many LDLs in the blood, because once all of the cells’ needs are met, and their blood cholesterol doors disappear, the LDL in the bloodstream has no destination, so it gets deposited in and around smooth muscle fibers, which creates atherosclerotic plaque, which contributes to heart disease.

There is another not-so-common way to end up with too many LDLs in the blood.  If a person has too few LDL receptors – their cells don’t make enough “blood cholesterol doors”.

Good cholesterol

Our livers also make High Density Lipoproteins (HDLs), one of the other parts of blood cholesterol.  The role of HDLs is to remove excess cholesterol from body cells and from the blood and transport it to the liver for elimination.  So the HDL boats go through the bloodstream and pick up excess cholesterol and drop it off at the liver.

HDL is what is known as the “good cholesterol”.  The way I remember which is the “good” and which is the “bad” is this:

Low Density Lipoproteins (LDL), are Low quality lipoproteins.  High Density Lipoproteins (HDL), are High quality lipoproteins.  We don’t want low quality, we want high quality, “H” for High, so HDL is the good one.

Note: Of the two most common blood measurements, blood pressure and cholesterol, blood pressure is by far the more important to your health.  High blood pressure is definitely a risk to health; high blood cholesterol may or may not be a health risk.


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