Influence of trans fatty acids on linoleic acid metabolism in the rat

At the start of the work described in this thesis, most reviewers on trans fatty acids agreed that these isomeric fatty acids did not induce undesirable effects, provided sufficient linoleic acid was present in the diet (Beare-Rogers, 1983; Emken, 1983; Gottenbos, 1983; Gurr, 1983). However, trans fatty acids were reported to aggravate symptoms of essential fatty acid deficiency in experimental animals (poor growth, deteriorated skin, impairment of spermatogenesis) and cause alterations in tissue fatty acid composition and decrease prostaglandin synthesis (Aaes-J0rgensen and H0lmer, 1969; Hill et al, 1979; Kinsella et al, 1981). It was our aim to define the minimum requirement for linoleic acid necessary to prevent specific or adverse effects (like aggravation of linoleic acid deficiency and decrease in prostaglandin synthesis) of trans fatty acids from partially hydrogenated vegetable oils (mainly Cl8 trans fatty acids) . Moreover, we wanted to get a better insight into the effects of trans fatty acids on linoleic acid metabolism, because it was suggested that changes in metabolism of linoleic acid and polyunsaturated fatty acids derived thereof could be the underlying cause of the alleged adverse effects of trans fatty acids (Kinsella et al, 1981; Hill et al, 1982). In our feeding experiments we used a special, partially hydrogenated soybean oil. This oil contained a high amount of various monoenoic trans isomers, but also a relatively high amount of dienoic trans fatty acids: isomers of linoleic acid. The diets were composed in such a way as to contain 16 en% trans monoenes and maximally about 3.2 en% trans dienes (about 0.2 en% 9t,l2t-18:2 and 0.2 en% other 9,12-18:2 isomers and 3.1 en% non-9,12-18:2 isomers (cis and trans)), thus by far exceeding the trans content of human diets. The advantage of this approach over feeding isolated fatty acids is that both monoenoic and polyenoic trans fatty acids are present in the experimental diet and that the distribution of positional isomers is similar to that in the human diet. So, conclusions can be reached with regard to the nutritive value of trans fatty acidscontaining food products, consumed in realistic amounts