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FATS AND CHOLESTEROL
Cholesterol plays both a vital and a detrimental role in your health. It is
essential for good health, but it does not need to be obtained from your diet,
your body can manufacture the cholesterol it needs from simpler substances which
it derives from the breakdown of fats, sugars and proteins. It is interesting
to note that your body needs cholesterol. It is a vital and essential part of
your diet. If you restrit and try to lower your incoming cholesterol you will
find that your body metabolises and creates its own cholesterol itself. Your
aim is to learn the difference between high density lipoproteins (HDL) cholesterol
and low density lipoporteins (LDL) cholesterol, to understanding the good and
the bad sides of cholesterol and how it affects your body.
Vital Functions of Cholesterol
-compensates for the changes in membrane fluidity keeping it within the narrow
limits required for optimal membrane function.
-the body makes steroid hormones from cholesterol
-the body makes adrenal corticosteroid hormones from cholesterol, eg. aldosterone
which regulates water balance through the kidneys
-allows the body to make vitamin D
-bile acids are derived from cholesterol
-it is also secreted by glands in our skin to protect against dehydration and
infection
Body Content
The average person's body has about 150g of cholesterol, most of which is found
in the membranes and about 7g in the blood.
Removal
Cholesterol is unique in that our body can make it but once made it cannot break
it down therefore it must be removed from the body through excretion. This removal
is increased by high levels of dietary fibre.
Atherosclerosis
These are deposits of proteins, fats, cholesterol and minerals in the arteries.
They narrow the arteries and slow down blood flow. Excess cholesterol also makes
platelets sticky which can lead to blood clots.
Cholesterol deposits also "harden" the arteries leading to high blood
pressure because the arteries resilience which normally takes up the pressure
generated by each heartbeat is lost.
HDL and LDL - the differences
Cholesterol is unique in that our bodies can make it but once made, cannot break
it down. By contrast sugars, fats, amino acids, and nucleic acids can all be
taken apart and turned into carbon dioxide, water and ammonia. As a result of
this perculiarity, cholesterol must (and can only) be removed from our bodies
through our stool (in the form of bile acids and cholesterol molecules).
The removal of cholesterol is increased by fibre. If fibre is absent, upto
94% of the cholesterol and bile acids are reabsorbed and recycled. This is why
low fibre diets can increase blood cholesterol levels.
The average person contains about one third of a pound of cholesterol (thats
150 grams or 5 ounces.) Most of this is found in the membranes, and baout 7
grams is carried in our blood. The daily turnover of cholesterol is about 1
gram. This cholesterol is carried around in our bodies by a vehicle carrier
called plasma lipoproteins.
The two different groups of lipoproteins play different roles. One fraction,
made up of four sub fractions, the most prominent of which is called low density
lipoprotein (LDL - sometimes called bad cholesterol) carries cholesterol and
triglycerides (fats) from foods and our liver to our cells. the other fraction
is called high density lipoprotein (HDL - sometimes called good cholesterol)
carries cholesterol from cells back to our liver, where that organ changes cholesterol
to bile, excretes both into our intestines, and eventually discards them with
our stool. Total blood cholesterol is all cholesterol in transit, being carried
by different lipoprotein vehicles, to and from our cells.
Cholesterol And Heart Disease
The stickiness of saturated fats and cholesterol is only one factor in cardiovascular
disease. The complete story is a little more complex. There is injury to the
lining of the artery, due to toxic free radical damage, oxidized LDL cholesterol,
oxidized triglyceride fatty acids, etc. This is followed by attempts at repair
that involve thickening the arteries by repair proteins apo(a) and fibrinogen,
along with fats and cholesterol. The combination of thickened (narrowed) arteries
and sticky platelets sets the stage for heart attacks, strokes and emboli.
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