The following abstracts of the research of lipidologist ML Garg
contradict Udo Erasmus's claim that SFAs interfere with EFA
utilization.

Todd Moody
[log in to unmask]
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J Lipid Res 1990 Feb;31(2):271-277

Interactions of saturated, n-6 and n-3 polyunsaturated fatty
acids to modulate arachidonic acid metabolism.

Garg ML, Thomson AB, Clandinin MT

Nutrition and Metabolism Research Group, University of Alberta,
Edmonton, Canada.

Anti-thrombotic effects of omega-3 (n-3) fatty acids are believed
to be due to their ability to reduce arachidonic acid levels.
Therefore, weanling rats were fed n-3 acids in the form of
linseed oil (18:3n-3) or fish oil (containing 20:5n-3 and
22:6n-3) in diets containing high levels of either saturated
fatty acids (hydrogenated beef tallow) or high levels of linoleic
acid (safflower oil) for 4 weeks. The effect of diet on the
rate-limiting enzyme of arachidonic acid biosynthesis (delta
6-desaturase) and on the lipid composition of hepatic microsomal
membrane was determined. Both linseed oil- or fish oil-containing
diets inhibited conversion of linoleic acid to gamma-linolenic
acid. Inhibition was greater with fish oil than with linseed oil,
only when fed with saturated fat. delta 6-Desaturase activity was
not affected when n-3 fatty acids were fed with high levels of
n-6 fatty acids. Arachidonic acid content of serum lipids and
hepatic microsomal phospholipids was lower when n-3 fatty acids
were fed in combination with beef tallow but not when fed with
safflower oil. Similarly, n-3 fatty acids (18:3n-3, 20:5n-3,
22:5n-3, and 22:6n-3) accumulated to a greater extent when n-3
fatty acids were fed with beef tallow than with safflower oil.
These observations indicate that the efficacy of n-3 fatty acids
in reducing arachidonic acid level is dependent on the linoleic
acid to saturated fatty acid ratio of the diet consumed.


Lipids 1989 Apr;24(4):334-9


Dietary saturated fat level alters the competition between alpha-linolenic and
linoleic acid.

Garg ML, Wierzbicki AA, Thomson AB, Clandinin MT

Department of Foods and Nutrition, University of Alberta, Edmonton, Canada.

Male weanling rats were fed semi-synthetic diets high in saturated fat (beef
tallow) vs high in linoleic acid (safflower oil) with or without high levels of
alpha-linolenic acid (linseed oil) for a period of 28 days. The effect of
feeding these diets on cholesterol content and fatty acid composition of serum
and liver lipids was examined. Feeding linseed oil with beef tallow or
safflower oil had no significant effect on serum levels of cholesterol. Serum
cholesterol concentration was higher in animals fed the safflower oil diet than
in animals fed the beef tallow diet without linseed oil. Feeding linseed oil
lowered the cholesterol content in liver tissue for all dietary treatments
tested. Consumption of linseed oil reduced the arachidonic acid content with
concomitant increase in linoleic acid in serum and liver lipid fractions only
when fed in combination with beef tallow, but not when fed with safflower oil.
Similarly, omega 3 fatty acids (18:3 omega 3, 20:5 omega 3, 22:5 omega 3, 22:6
omega 3) replaced omega 6 fatty acids (20:4 omega 6, 22:4 omega 6, 22:5 omega
6) in serum and liver lipid fractions to a greater extent when linseed oil was
fed with beef tallow than with safflower oil. The results suggest that the
dietary ratio of linoleic acid to saturated fatty acids or of 18:3 omega 3 to
18:2 omega 6 may be important to determine the cholesterol and arachidonic acid
lowering effect of dietary alpha-linolenic acid.

PMID: 2569150, UI: 89330117

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