by Stacey J. Bell, D.Sc., R.D.
The body can make most of the twenty or so fats that we
normally consume. Only two fats are essential - omega-
6s and omega-3s, and these polyunsaturated fatty acids
must be obtained from diet or from supplements. The
omega-3 fatty acids include the long-chain fatty acids
eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)
and ??-linolenic acid (ALA). These essential fats get stored
as phospholipids on the cell membranes and then serve
as precursors for many biological functions. Within the past
100 years, the consumption of total fat and omega-6 has
increased, while the intake of omega-3s has decreased.
Various authorities consider the modern increase in the
consumption of omega-6 fatty acids and the vastly increased
ratio of omega-6 to omega-3 ingestion to be a root cause of
chronic activation of inflammatory responses.
Omega-3 fatty acids are distinguished by their molecular
structure. Fats are long chains of carbon atoms. The
"omega" refers to the place along the chain where the first
double bond connects the carbons (see figure). Starting
from the methyl end (CH3 or omega end) of the chain,
the place where the first double bond is placed defines
a "family" of similar fats. Omega-3s have the first double
bond between the third and fourth carbon atoms. Marine
animals supply mostly EPA and DHA and some plants (fl ax,
canola, soy oils) provide dietary sources of ALA.
ALA from plant oils must be elongated (more carbon atoms
added) and desaturated (more double-bonds between
the carbons added) before this omega-3 fatty acid can be
utilized for many purposes in the body. Conversion to the
bioactive form is poor; only about 10% of ALA makes it to
a bioactive state.
The Food and Drug Administration on September 8,
2004 gave "qualified health claim" status to EPA and
DHA omega-3 fatty acids because "supportive but not
conclusive research shows that consumption of EPA and
DHA [n-3] fatty acids may reduce the risk of coronary heart
disease." The omega-3 fatty acids also are essential for
normal growth in young children. A great deal of evidence
also supports roles for the omega-3 fatty acids, especially
EPA and DHA, in boosting brain function and promoting