Nutrition Science and Everyday Application - beta v 0.1

272 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
found in salad dressings and margarine. Rich food sources of alpha-linolenic acid (ALA)
include nuts, flaxseed, whole grains, legumes, and dark green leafy vegetables.
Figure 5.18. The chemical structure of the essential fatty acids shown in shorthand, without
individual carbon and hydrogen atoms marked.
Most Americans easily consume enough linoleic acid and other omega-6 fatty acids,
because corn and soybean oil are common ingredients in our food supply. However, sources
of ALA and other omega-3 fatty acids are less common in the American diet, and many
people could benefit from incorporating more sources of these into their diet. As an added
benefit, whole foods rich in ALA come packaged with other healthful nutrients, like fiber,
protein, vitamins, minerals, and phytochemicals.
A true essential fatty acid deficiency is rare in the developed world, but it can occur,
usually in people who eat very low-fat diets or have impaired fat absorption. Symptoms
include dry and scaly skin, poor wound healing, increased vulnerability to infections, and
impaired growth in infants and children. 1
Omega-3 and omega-6 fatty acids are precursors to a large family of important signaling
molecules called eicosanoids (prostaglandins are one type of eicosanoid). Among the many
functions of eicosanoids in the body, one of the most important is to regulate inflammation.
Without these hormone-like molecules, the body would not be able to heal wounds or fight
off infections each time a foreign germ presented itself. In addition to their role in the
body’s immune and inflammatory processes, eicosanoids also help to regulate circulation,
respiration, and muscle movement.
Eicosanoids derived from omega-6 fatty acids tend to increase blood pressure, blood
clotting, immune response, and inflammation. These are necessary functions, but they
can be associated with disease when chronically elevated. In contrast, eicosanoids derived
from omega-3 fatty acids tend to lower blood pressure, inflammation, and blood clotting,
functions that can benefit heart health. Omega-3 and omega-6 fatty acids compete for the
same enzymatic pathways in the formation of different eicosanoids, so increasing omega-3
fatty acids in the diet may have anti-inflammatory effects.
Two additional omega-3 fatty acids with important health benefits are eicosapentaenoic