Consumer
Guide To Fats - Types of Fat
Here are brief definitions of the key terms important to
an understanding of the role of fat in the diet.
Cholesterol:
A chemical compound manufactured in the body. It is used
to build cell membranes and brain and nerve tissues. Cholesterol
also helps the body make steroid hormones and bile
acids.
Dietary cholesterol:
Cholesterol found in animal products that are part of the
human diet. Egg yolks, liver, meat, some shellfish, and whole-milk
dairy products are all sources of dietary cholesterol.
Fatty acid:
A molecule composed mostly of carbon and hydrogen atoms.
Fatty acids are the building blocks of fats.
Fat:
A chemical compound containing one or more fatty acids. Fat
is one of the three main constituents of food (the others
are protein and carbohydrate). It is also the principal form
in which energy is stored in the body.
Hydrogenated fat:
A fat that has been chemically altered by the addition of
hydrogen atoms (see trans fatty acid). Vegetable oil and margarine
are hydrogenated fats.
Lipid:
A chemical compound characterized by the fact that it is
insoluble in water. Both fat and cholesterol are members of
the lipid family.
Lipoprotein:
A chemical compound made of fat and protein. Lipoproteins
that have more fat than protein are called low-density lipoproteins
(LDLs). Lipoproteins that have more protein than fat are called
high-density lipoproteins (HDLs). Lipoproteins are found in
the blood, where their main function is to carry cholesterol.
Monounsaturated fatty acid:
A fatty acid that is missing one pair of hydrogen atoms in
the middle of the molecule. The gap is called an "unsaturation."
Monounsaturated fatty acids are found mostly in plant and
sea foods.
Monounsaturated fat:
A fat made of monounsaturated fatty acids. Olive oil and
canola oil are monounsaturated fats. Monounsaturated fats
tend to lower levels of LDL-cholesterol in the blood.
Polyunsaturated fatty acid:
A fatty acid that is missing more than one pair of hydrogen
atoms. Polyunsaturated fatty acids are mostly found in plant
and sea foods.
Polyunsaturated fat:
A fat made of polyunsaturated fatty acids. Safflower oil
and corn oil are polyunsaturated fats. Polyunsaturated fats
tend to lower levels of both HDL-cholesterol and LDL-cholesterol
in the blood.
Saturated fatty acid:
A fatty acid that has the maximum possible number of hydrogen
atoms attached to every carbon atom. It is said to be "saturated"
with hydrogen atoms. Saturated fatty acids are mostly found
in animal products such as meat and whole milk.
Saturated fat:
A fat made of saturated fatty acids. Butter and lard are
saturated fats. Saturated fats tend to raise levels of LDL-cholesterol
("bad" cholesterol) in the blood. Elevated levels
of LDL-cholesterol are associated with heart disease.
Trans fatty acid:
A polyunsaturated fatty acid in which some of the missing
hydrogen atoms have been put back in a chemical process called
hydrogenation. Trans fatty acids are the building blocks of
hydrogenated fats. n
Dietary guidelines endorsed by the U.S. Department of Agriculture
and the U.S. Department of Health and Human Services advise
consumers to:
Reduce total dietary fat intake to 30 percent or less of
total calories.
Reduce saturated fat intake to less than 10 percent of calories.
Reduce cholesterol intake to less than 300 milligrams daily.
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