Cholesterol - The Non Storybook Version
By now
you have probably all heard of “the good cholesterol” and “the
bad cholesterol”. I am
referring to the storybook version of the beneficial and detrimental
effects of cholesterol. I
remember some years ago when I was studying for my master’s degree,
my major professor, a comparative endocrinologist, returned from
seeing his physician for a general checkup.
This included a blood test to measure his lipid (fat) blood
levels, which in turn included testing his various cholesterol levels.
As he told me the story he chided this man for presenting an
embarrassingly over-simplified, storybook version of lipid physiology
describing his cholesterol as “the good cholesterol” and “the
bad cholesterol”. A few
years later I read a medical essay in a supplement to the Mayo
Clinic Health Letter. It
stated, “My doctor gave me the results of my cholesterol test.
He said, ‘Your good cholesterol is low---that is bad, and
your bad cholesterol is high---that is bad too.
You need to raise your good and lower your bad---that would be
good’”. I believe
that this sort of explanation is not only insulting to the
intelligence of the listener, it is nothing less than confusing.
Since that time I vowed that I would never resort to the
“good and bad cholesterol” storytelling.
Cholesterol
is a waxy lipid that serves as an essential building material
throughout your body to build cell membranes and to insulate your
nerves. In addition, it
is the backbone molecule of certain hormones and it is also the
backbone molecule of bile acids produced by your liver, which help you
digest your food. About
80% of your blood cholesterol is produced in your liver and about 20%
comes from your diet, consequently the amount of fat and cholesterol
that you eat may influence blood lipid levels including your blood
cholesterol levels.
For
fats to be transported through your blood vascular system they must be
coated with protein and this coated molecule is referred to as
lipoprotein. Lipoproteins
are responsible for transporting blood lipids, cholesterol and
triglycerides in your blood vascular system.
Lipoproteins that carry these lipids may vary in density and
some are called low-density lipoproteins (LDLs) whereas others are
called high-density lipoproteins (HDLs) and there are very-low-density
lipoproteins (VLDL) as well. LDLs
bind to the surface of cells but if they are not used by the cell they
may saturate it with cholesterol, and this may in turn become
deposited within the walls of the cells lining your arteries resulting
in plaques that cause atherosclerosis (narrowing and blockage of the
artery).
Enlarging
plaques may cause the inner lining of your artery to become rough,
which may in turn cause a blood clot to form that severely narrows the
caliber of the blood vessel or completely plugs it, preventing blood
flow. When this occurs in one of the blood vessels in your heart it
results in a heart attack. If
it occurs in part of your brain it results in a brain attack, or
stroke. So, your blood
cholesterol levels are important since this is a significant risk
factor for heart blood vessel disease, which is still the number one
killer of Americans. Your
risk for heart and brain blood vessel disease can be significantly
lowered by keeping your cholesterol levels within normal ranges.
One of the ways that the body keeps cholesterol from damaging blood
vessels is by circulating HDLs, which pick up unused LDLs attached to
the surface of cells thereby preventing these from becoming deposited.
In fact, the ratio of LDL and HDL is very important and in
some cases more attention is being paid to the HDL level to be certain
that it is high enough to scavenge the excess LDLs.
The only way to know if your blood lipids are in the desirable
range is to have a blood test after you have fasted overnight. Your family physician or specialist can order this test and
help you interpret the results.
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