The present experiment was designed to comprehensively examine the eff
ect of feeding several dietary oils differing in chain length and in p
osition and number of double bonds of fatty acids on brain and heart f
atty acid composition of rats. Therefore, 110 male Sprague-Dawley rats
were initially fed a control diet with 10% coconut oil for 28 days; 1
0 groups of 10 rats each were then switched to semipurified test diets
for another 20 days containing 5% or 10% olive oil, safflower oil, ev
ening primrose oil, linseed oil or salmon oil for exchange of coconut
oil. Dietary test oils did not,have substantial effects on saturated f
atty acids (SFA) and monounsaturated fatty acids (MUFA) in brain. The
most striking changes provoked by dietary manipulation were observed o
n the n-6 and n-3 polyunsaturated fatty acids (PUFA). PUFA in rat brai
n were remarkable for its high levels of 20:4 n-6 and 22:6 n-3. n-6 PU
FA, respectively 18:2 n-6 and 20:4 n-6 were slightly, but significantl
y elevated after feeding safflower and evening primrose oil; in contra
st, linseed oil and salmon oil increased the proportion of long chain
n-3 PUFA at the expense of n-6 PUFA in brain compared to the control g
roup. The reduction in n-6 PUFA was mainly due to 22:5 n-6 and in the
case of salmon oil diets also 20:4 n-6 and 22:4 n-6 were consistently
lowered. In rat heart the amount of SFA was highest in control rats fe
d coconut oil. Both coconut oil and olive oil diets produced much high
er levels of MUFA, especially 18:1 in the heart than did the other die
ts. As in brain, the most marked variations in heart were observed on
n-6 and n-3 fatty acids. In contrast to brain lipids, rat heart was re
markable for its high proportions of 18:2 n-6 and 20:4 n-6. Both saffl
ower oil and evening primrose oil markedly increased 18:2 n-6, 22:4 n-
6 and 22:5 n-6 in rat hearts compared to the other diets. Conversely,
the addition of linseed oil and salmon oil lowered 20:4 n-6, 22:4 n-6
and 22:5 n-6, whereas, salmon oil had a stronger effect on 20:4 n-6 th
an linseed oil. A rise in all cardiac n-3 PUFA was found, however, lin
seed oil mainly increased 18:3 n-3 and 22:5 n-3 and salmon oil mainly
elevated 20:5 n-3 and 22:6 n-3. This inverse relationship between the
n-6 and n-3 PUFA suggests a competition between these fatty acids for
incorporation into brain and heart lipids.