Nutrition Science and Everyday Application - beta v 0.1

FATTY ACID TYPES AND FOOD SOURCES 271
Figure 5.16. Examples of foods high in polyunsaturated fats, like fish and nuts
OMEGA-3, OMEGA-6, AND ESSENTIAL FATTY ACIDS
In addition to the length of the carbon chain and the number of double bonds, unsaturated
fatty acids are also classified by the position of the first double bond relative to the
methyl (-CH 3 ) or “omega” end of the carbon chain (the end furthest from the glycerol
backbone in a triglyceride). Fatty acids with the first double bond at the third carbon from
the omega end are called omega-3 fatty acids. Those with the first double bond at the sixth
carbon from the omega end are called omega-6 fatty acids. (There are also omega-9 fatty
acids.)
Figure 5.17. The position of the first C=C double bond determines whether an unsaturated fatty
acid is classified as omega-3 or omega-6. The two essential fatty acids, linoleic acid (an omega-6)
and alpha-linolenic acid (an omega-3) are shown here.
Fatty acids are vital for the normal operation of all body systems, but the body is capable
of synthesizing most of the fatty acids it needs. However, there are two fatty acids that the
body cannot synthesize: linoleic acid (an omega-6) and alpha-linolenic acid (ALA, an omega-3).
These are called essential fatty acids because they must be consumed in the diet. Other fatty
acids are called nonessential fatty acids, but that doesn’t mean they’re unimportant; the
classification is based solely on the ability of the body to synthesize the fatty acid. Excellent
food sources of linoleic fatty acid include plant oils such as corn oil and soybean oil, often