Cholesterol is a waxy, fat-like substance that is made in the
body by the liver. Cholesterol forms part of every cell in the
body and serves a number of vital functions.
The heart pumps blood through blood vessels called arteries.
This blood carries vital oxygen and nutrients needed by tissues
and organs throughout the body. The heart itself is supplied with
blood vessels called coronary arteries. When cholesterol levels
rise above normal limits and stay high, some cholesterol is left
behind in the arteries. Over the years, a hardened, waxy substance
called cholesterol plaque builds up on the artery walls, and reduces
or blocks blood flow. Organs supplied by these arteries then become
damaged because they cannot get the oxygen and nutrients they
need. For example, when blood flow to the brain is blocked, a
stroke occurs. When plaque completely blocks a coronary artery,
a heart attack takes place.
Cholesterol in the body comes from two sources. Most cholesterol
is made by the liver from various nutrients and especially from
saturated fats. The liver makes just about all the cholesterol
the body will ever need. Since all animals can make their own
cholesterol, some cholesterol in the human body comes directly
from eating animal products. These foods include meats, egg yolks,
organ meats, whole milk and milk products. This cholesterol is
absorbed through the intestines and added to what the liver makes.
It is also known that a diet high in saturated fat seems to increase
cholesterol production in the body. Therefore, reducing dietary
cholesterol and fats helps to keep blood cholesterol levels within
a healthy range.
Our body does need cholesterol to make bile salts, hormones and
vitamin D. It is mainly produced by our liver. Cholesterol will
build up on the artery walls when the level of cholesterol in
the blood is too high. There are 2 main types of blood cholesterol:
LDL (the "Bad" cholesterol) and HDL (the "Good"
cholesterol).
High amounts of the bad LDL will deposit cholesterol on the artery
walls forming plaques. More and more plaques will narrow the arteries
lumen and may eventually block blood flow. Therefore LDL is considered
the "Bad" cholesterol. Saturated fats and trans fattty
acids are the most important factors that raise blood cholesterol,
not dietary cholesterol! Monounsaturated fats and polyunsaturated
fats found in nuts and fish for instance, can lower the LDL level.
In addition, soluble fiber found in fruits, oats, barley and legumes
can also lower LDL.
The good HDL, on the other hand, takes excess cholesterol away
and carries it back to the liver to be excreted. It can also remove
some of the cholesterol already attached to the artery walls.
Therefore HDL is considered the "Good" cholesterol as
high levels of HDL in the blood can decrease the risk of heart
disease. Physical activity can also raise HDL level.
