Dietary Fats Are Not Created Equal
Understanding the different types of fats can be difficult
for the consumer. Since not all fats are created equal in
health, it is important to understand the differences in
dietary fats; healthy versus unhealthy.
Triglycerides (triacylglycerols) are an important class of
dietary fats. The triglyceride consists of a molecule of
glycerol and three molecules of fatty acids. Biologic
properties of triglycerides are determined by the presence
or absence of double bonds, the number and location of
double bonds, and the configuration (cis, trans) of the
unsaturated fatty acid. Fatty acids consist of a
hydrocarbon chain (C-H) with a carboxyl group (COOH) at one
end. The glycerol molecule contains three hydroxyl groups
Much of the fat in the body is in the form of
triglycerides. Many of the foods we eat also contain
triglycerides. Elevated triglyceride levels in the blood
have been linked to an increased risk of heart disease.
These triglycerides are not directly from dietary fats but
made in the liver from excess sugars that have not been
used for energy. The excess sugar source is from foods
containing carbohydrates such as refined sugar and white
Saturated fats are a type of triglyceride. This
triglyceride contains primarily fatty acids whose side
chains do not contain any double bonds. These fats are
characteristically called saturated because all available
carbon bonds are occupied by a hydrogen atom. Saturated
fats are highly stable and can resist oxidation. The
saturated fat molecule is straight in form. Hence,
saturated fats form a solid or semisolid at room
temperature. Main sources of saturated fats are meat and
dairy products, and a few vegetable oils (palm and coconut
oils). A diet high in saturated fat is associated with an
increased risk of heart disease.
Monounsaturated fats are another type of triglyceride. The
fatty acids contain only one double bond. A few sources of
monounsaturated fats are olive, peanut, and rapeseed
(canola) oil. This type of fat has the ability to
favorably modify lipoprotein levels. A good example of a
diet high in monounsaturated fat is the Mediterranean diet.
The Mediterranean cultures show that a diet rich in olive
oil is correlated with a low incidence of heart disease.
Polyunsaturated fats are a type of triglyceride in which
the fatty acids contain more than one double bond. Double
bonds in natural fats are rigid and introduce a kink in the
molecule. This kink prevents the fatty acids from packing
close together. As a result, unsaturated fats have a lower
melting point than saturated fats. Most unsaturated fats
are liquid at room temperature and referred to as oils.
The effect that the polyunsaturated fat has on heart
disease is influenced by the location of the double bond
within the molecule. Omega-6 fatty acids (n-6 fatty acids)
are a type of polyunsaturated fat. The omega-6 fatty acid,
primarily linoleic acid obtained from vegetable oils
protects against heart disease. Good sources of omega-6
fats are nuts, avocados, olives, soybeans, along with
sesame, cottonseed, and corn oil.
Omega-3 fatty acids (n-3 fatty acids) are a type of
polyunsaturated fat. The omega-3 fatty acid is primarily
linolenic acid. These fatty acids are found primarily in
plants and in fish oils that contain DHA (docosahexaenoic
acid) and EPA (eicosapentaenoic acid). Omega-6 and omega-3
fats are considered essential fatty acids. These fatty
acids are associated with a lowered risk of heart disease.
Trans fatty acids are chemically unsaturated fatty acids.
However, in the body trans fatty acids behave much like
saturated fatty acids. Why is this bad? Trans fatty acids
increase serum low density lipoproteins (LDL’s) but not
high density lipoproteins (HDL’s). With the shift in LDL
levels, Trans fats increase the risk of heart disease.
Trans fats can be introduced into the diet in ways most are
unaware of. During hydrogenation, polyunsaturated oils
become exposed to hydrogen at high temperatures. The
nature of the polyunsaturated fat becomes transformed into
a trans fat. Most margarines and baked goods contain the
hydrogenated polyunsaturated oils. Trans fats should be
avoided at all costs.
Dietary fats are not created equal. The common diet
conscious individual avoids any and all dietary fat. Some
dietary fats are necessary for life. With a more specific
dietary fat watch on the mind, the right food choices can
be easier for a heart healthy dieter.
Copyright 2005 Kristy Haugen
About the Author:
Kristy Haugen is a Biology/Chemister bachelor degree
graduate working to make you a more informed consumer.
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