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 amount
