IX. RESEARCH SHOWING BENEFICIAL EFFECTS OF EATING THE MORE SATURATED FATS

One major concern expressed by the nutrition community is related to whether or not people are getting enough elongated omega-3 fatty acids in their diets. The elongated omega-3 fatty acids of concern are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Some research has shown that (the basic omega-3 fatty acid) -linolenic acid is not readily converted to the elongated forms in humans or animals, especially when there is ingestion of the trans fatty acids and the consequent inhibition of the delta-6-desaturase enzyme. One recent study (Gerster 1998), which used radioisotope-labeled -linolenic acid to measure this conversion in adult humans, showed that if the background fat in the diet was high in saturated fat, the conversion was approximately 6% for EPA and 3.8% for DHA, whereas if the background fat in the diet was high in omega-6 polyunsaturated fatty acids (PUFA), the conversion was reduced 40-50%.

Nanji and colleagues (1995) report that a diet enriched in saturated but not unsaturated fatty acids reversed alcoholic liver injury in their animals, which was caused by dietary linoleic acid. These researchers conclude that this effect may be explained by the down-regulation of lipid peroxidation. This is another example of the need for adequate saturated fat in the diet. Cha and Sachan (1994) studied the effects of saturated fatty acid and unsaturated fatty acid diets on ethanol pharmacokinetics. The hepatic enzyme alcohol dehydrogenase and plasma carnitines were also evaluated. The researchers concluded that dietary saturated fatty acids protect the liver from alcohol injury by retarding ethanol metabolism, and that carnitine may be involved.

Hargrove and colleagues (1999) noted the work of Nanji et al and postulated that they would find that diets rich in linoleic acid would also cause acute liver injury after acetaminophen injection. In the first experiment, two levels of fat (15 g/100 g protein and 20 g/100 g protein) were fed using corn oil or beef tallow. Liver enzymes indicating damage were significantly elevated in all the animals except for those animals fed the higher level of beef tallow. These researchers concluded that "diets with high [linoleic acid] may promote acetaminophen-induced liver injury compared to diets with more saturated and monounsaturated fatty acids."

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