Heart pathology in rats fed partially hydrogenated fish oil, rapeseed oil or peanut oil for 30 weeks.

132 male Sprague-Dawley rats were given diets for 30 weeks including rapeseed oil with 41.4% erucic acid, partially hydrogenated fish oil with 15.1% docosenoic acids, or peanut oil with no docosenoic acids. Four diets were isocaloric and contained respectively 21% rapeseed oil (8.7% w/w erucic acid), 10.5% rapeseed oil and 10.5% peanut oil (4.4% w/w erucic acid), 21% partially hydrogenated fish oil (3.2% w/w docosenoic acids) and 21% peanut oil. The fifth diet contained 4.3% peanut oil. The relative heart weights increased in rats fed rapeseed oil and partially hydrogenated fish oil, and abnormally enlarged hearts were found in 32% of the rats fed 21% rapeseed oil and in 5% of those fed 10.5% rapeseed oil. Heart lesions consisting of focal or confluent destruction of muscle cells were seen in all groups. The incidence was 96% and the average severity grade 2.5 when 21% rapeseed oil was given, and 61% and 1.3 respectively when 10.5% rapeseed oil was given. Minor heart lesions were found in 14% of the rats fed 21% partially hydrogenated fish oil, in 39% of those fed 21% peanut oil and in 12% when 4.3% peanut oil was given. It is concluded that partially hydrogenated fish oil is markedly less cardiopathogenic than high erucic rapeseed oil. The heart lesions that were found do not differ in incidence, severity or morphology from those found when peanut oil was given, or from those reported when other control fats and oils are given to rats for prolonged feeding periods.