Omega-3 Fatty Acids
Heart Attack Prevention Series
Medical Author Revision: Dennis Lee, M.D.,
Daniel Kulick, M.D.
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
What are fats, fatty acids, and omega-3 fatty acids?
Fat (also known as lipid) is one of the three classes of nutrients. The other
two are proteins and carbohydrates. The major function of fat is to provide
energy for the body. Pound per pound, fat contains more energy (calories) than
protein and carbohydrates. There are three types of fat; triglycerides,
cholesterol, and phospholipids.
Fatty acids consist of chains of carbon atoms linked together by chemical
bonds. On one end (terminal) of the carbon chain is a methyl group (a cluster of
carbon and hydrogen atoms). On the other terminal is a carboxyl group (a cluster
of carbon, oxygen and hydrogen atoms). The chemical bonds between carbon atoms
can be either single or double bonds. Single bonds have more hydrogen molecules
around them than double bonds. These chemical bonds determine whether a fatty
acid is saturated or unsaturated (see discussion below). Fatty acids also come
in different lengths: short chain fatty acids have fewer than 6 carbons, while
long chain fatty acids have 12 or more carbons.
Fatty acids serve as energy for
the muscles, heart, and other organs as building blocks for cell membranes and
as energy storage for the body. Fatty acids that are not used up as energy are
converted into triglycerides. A triglyceride is a molecule formed by attaching
three fatty acids onto a glycerol compound that serves as a backbone.
Triglycerides are then stored in the body as fat (adipose) tissue.
Saturated fatty acids contain single bonds only. Fats containing saturated
fatty acids are called saturated fats. Examples of foods high in saturated fats
include lard, butter, whole milk, cream, eggs, red meat, chocolate, and solid
shortenings. An excess intake of saturated fat can raise blood cholesterol and
increase the risk of developing coronary heart disease.
Monounsaturated fatty acids contain one double bond. Examples of foods high
in monounsaturated fat include avocados, nuts, and olive, peanut, and canola
oils. Scientists believe that increased consumption of monounsaturated fats (for
example, eating more nuts) is beneficial in lowering LDL cholesterol (the "bad"
cholesterol) and lowering the risk of coronary heart disease, especially if
monounsaturated fats are used to substitute for saturated fats and refined
Polyunsaturated fatty acids contain more than one double bond. Examples of
foods high in polyunsaturated fats include vegetable oils, corn, sunflower, and
Essential fatty acids are polyunsaturated fatty acids that the human body
needs for metabolic functioning but cannot produce, and therefore has to be
acquired from food.
Omega-3 fatty acids are a class of essential polyunsaturated
fatty acids with the double bond in the third carbon position from the methyl
terminal (hence the use of "3" in their description). Foods high in omega-3
fatty acids include salmon, halibut, sardines, albacore, trout, herring, walnut,
flaxseed oil, and canola oil. Other foods that contain omega-3 fatty acids
include shrimp, clams, light chunk tuna, catfish, cod, and spinach.
Omega-6 fatty acids are a class of essential polyunsaturated fatty acids with
the initial double bond in the sixth carbon position from the methyl group
(hence the "6"). Examples of foods rich in omega-6 fatty acids include corn,
safflower, sunflower, soybean, and cottonseed oil.
Omega-3 and omega-6 fatty
acids are also referred to as n-3 and n-6 fatty acids, respectively.
acids (trans fats) are made through hydrogenation to solidify liquid oils.
Heating omega-6 oils, such as corn oil, to high temperatures creates trans fats.
Trans fats increase the shelf life of oils and are found in vegetable
shortenings and in some margarines, commercial pastries, fried foods, crackers,
cookies, and snack foods. The intake of trans fatty acids increases blood
LDL-cholesterol ("bad" cholesterol), decreases HDL cholesterol ("good
cholesterol"), and raises the risk of coronary heart disease.