Fats, Fish Oil and Omega-3-Fatty Acids
Medical Author: Dennis Lee, M.D.
Medical Author: Gregory Thomas, M.D.
What is fat?
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:
- cholesterol, and
Triglycerides are where most of the fat calories
are stored. In addition to providing energy, fat also serves other functions,
for example, cholesterol and phospholipids are components of cell membranes and
sheaths surrounding nerve cells. Cholesterol is also important for the
production of bile acids and other hormones (such as sex hormones and adrenal
What are fatty acids?
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), 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 less 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. Those
fatty acids 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.
What are saturated fatty acids?
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. Excess intake of saturated fat can raise one's blood cholesterol
and increase the risk of developing coronary artery disease.
What are monounsaturated fatty acids?
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 sugars.
What are polyunsaturated fatty acids?
Polyunsaturated fatty acids contain more than one double bond. Examples of
foods high in polyunsaturated fats include vegetable oils, corn, sunflower, and
What are essential fatty acids?
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.
What are omega-3 fatty acids?
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.