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Omega
Omega-3/Omega-6
fatty acid content of Grass Fed Beef:
C.A. Daley1, A. Abbott1,
M. Basurto1, G. Nader2,
and S. Larson2
College of Agriculture, California State University, Chico1
University of California Cooperative Extension Service2
Omega-3/Omega-6:
Omega-3 fatty acids are considered essential fatty acids (EFA),
which means that they are essential to human health but cannot
be manufactured by the body. For this reason, omega-3 fatty
acids must be obtained from food.
Essential fatty acids are polyunsaturated and grouped into
two families, the omega-6 EFAs and the omega-3 EFAs. Although
there are just minor differences in their molecular structure
the two EFA families act very differently in the body. While
the metabolic products of omega-6 acids promote inflammation,
blood clotting, and tumor growth, the omega-3 acids act entirely
opposite. It is important to maintain a balance of omega-3
and omega-6 in the diet as these two substances work together
to promote health.
There are 3 major types of omega-3 fatty acids that are ingested
in foods and used by the body: alpha-linolenic acid (ALA),
eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
Once eaten, the body converts ALA to EPA and DHA, the two
types of omega-3 fatty acids more readily used by the body.
"Extensive research indicates that omega-3 fatty acids
reduce inflammation and help prevent certain chronic disease
such as heart disease and arthritis. These essential fatty
acids are highly concentrated in the brain and appear to be
particularly important for cognitive and behavioral function
(University of Maryland, College of Medicine)."
According to the University of Maryland, an inappropriate
balance of these essential fatty acids (high omega-6/omega-3
ratio) contributes to the development of disease while a proper
balance helps maintain and even improves health. A healthy
diet should consist of roughly one to four times more omega-6
fatty acids than omega-3 fatty acids. The typical American
diet tends to contain 11 to 30 times more omega-6 fatty acids
than omega-3 and many researchers believe this imbalance is
a significant factor in the rising rate of inflammatory disorders
in the United States.
Scientists discovered the many benefits of EPA and DHA in
the early 1970's when Danish physicians observed that Greenland
Eskimos had an exceptionally low incidence of heart disease
and arthritis despite the fact that they consumed a high-fat
diet. More recent research has established that EPA and DHA
play a crucial role in the prevention of atherosclerosis,
heart attack, depression and cancer (Simopoulos, 1991; Simopoulos
2002; Connor, 2000). In addition, omega-3 consumption by individuals
with rheumatoid arthritis has led to the reduction or discontinuation
of their ordinary treatment (Kremer, 1989; DiGiacomo, 1989).
The human brain has a high requirement for DHA. Low DHA levels
have been linked to low brain serotonin levels, which are
connected to an increased tendency for depression and suicide.
Several studies have established a clear association between
low levels of omega-3 fatty acids and depression. In fact,
countries with a high level of omega-3 consumption have fewer
cases of depression, decreased incidence of age-related memory
loss as well as a reduction in impaired cognitive function
and a lower risk of developing Alzheimer's disease (Kalmijn
et al., 1997a; Kalmijn et al., 1997b; Yehuda et al., 1996;
Hibbeln, 1998; Hibbeln et al., 1995; Stoll et al., 1999; Calabrese
et al., 1999; Laugharne et al., 1996).
Many scientists believe that increases in these chronic diseases
are no accident, it is directly related to the change in our
dietary patterns over the last 200 years. Our ancestors lived
on an omega-6:omega-3 ratio of 1:1, while our current dietary
habits are closer to 10-20:1 (Simopoulos, 1991; Pepping, 1999).
Researchers believe the ideal omega-6 intake should be no
more than 4-5 times that of our omega-3 intake. The National
Institutes of Health recently published recommended daily
intakes of fatty acids, specific recommendations include 650
mg of EPA and DHA, 2.22 g/day of alpha-linolenic acid and
4.44 g/day of linoleic acid.
Diet can significantly alter the fatty acid composition in
fed cattle. Cattle fed primarily grass enhanced the omega-3
content of beef by 60% and also produces a more favorable
omega-6 to omega-3 ratio. Conventional beef contains a 4:1
6:3 ratio while grass-only diets produce a 2:1 6:3 ratio (French
et al., 2000; Duckett et al., 1993; Marmer et al, 1984; Wood
and Enser, 1997). Values reported in Table 1 reflect the number
of grams/ 100 grams of fatty acids. |
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Table 1.
 The
amount of lipid in beef is highly variable depending on diet
and cut of beef. Estimates within the longissimus muscle range
from 40 to 100 mg/gram of tissue (French et al., 2000; Duckett
et al., 1993). When lipid content is standard, a serving of
grass-fed beef would provide 88.5 mg of omega-3, roughly 13%
of the RDI for EPA/DHA, while the conventional product would
supply an estimated 54.6 mg or 8% of RDI for omega-3.
More important is the ratio of omega-3 to omega-6. Both conventional
and grass-fed beef provide acceptable 6:3 ratios, however
grass-fed beef is closer to the ideal of a 1:1 ratio. Interestingly,
diet has little effect on the proportion of omega-6 fatty
acids, however the method of feeding did significantly alter
the omega-3 content of fed beef.
References
Contact information: C.A.Daley, Associate
Professor, College of Agriculture, California State University,
Chico, Chico CA 95929, cdaley@csuchico.edu.
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