ABOUT CHOLESTEROL
Cholesterol has become a household word because of evidence
indicating that excesses of it in the blood may play a part in producing
coronary atherosclerosis, the narrowing of the coronary arteries which may lead
to heart attacks. Cholesterol is present as such in some foods. It is also
produced by the body. Actually, the soft, waxy, yellowish substance is an
essential part of every body cell. It plays a basic role in the passage of
substances through cell walls.
One example of how cholesterol does this is readily
observable: when you put your hand into a basin of water, little of the water
soaks into the skin. The reason: cholesterol in the outer layer of skin cells
makes the skin impermeable to water.
Since the material is essential, the body is equipped to
produce a supply as well as use what comes in, ready-built, in food. The liver
can make cholesterol from molecules of acetyl coenzyme A, a chemical derived
from fats, carbohydrates, and proteins. It is not cholesterol per se but an
excess of it in the blood which is the danger factor.
And while an excess can
be traced to some extent to a diet heavy in foods rich in cholesterol, a
high-fat diet may raise blood cholesterol levels abnormally. This appears to be
due to increased deposits of fat in the liver, providing an increased source of
acetyl coenzyme A for liver manufacture of cholesterol.
Moreover, it is the nature of the fat in the diet that is
significant. Some types of fat, known as saturated, increase blood cholesterol
levels. Others, called unsaturated and polyunsaturated, do not-and, in fact,
tend to slightly decrease cholesterol levels. The difference between saturated
and unsaturated, from a chemist's viewpoint, is a matter of hydro-gen atoms:
saturated fats are saturated with, or full of, hydrogen atoms; unsaturated fats
have room for more hydrogen atoms.
In everyday terms, the primary saturated
fats are milk fat, meat fat, coconut oil, and cocoa fat.
Milk fat includes the
fat in butter, most cheeses, and ice cream as well as whole milk. Meat fat
means primarily the fat of beef, pork, and lamb; veal has less fat, and chicken
and turkey are low in fat and the fat they contain is less saturated.
Polyunsaturated fats are the liquid vegetable oils such as safflower, soybean,
corn, and cottonseed, the Food You Eat.
