Absorption of very-long-chain saturated fatty acids in totally hydrogenated fish oil

Abstract

Partially hydrogenated fish oil (PHFO) contains a high amount of trans fatty acids (TFA). Total hydrogenation results in a minimal amount of TFA, but a high content of very-long-chain saturated fatty acids (VLCSFA). Absorption and metabolism of VLCSFA from totally hydrogenated fish oil (THFO) were studied in rats. Groups of eight rats were fed one of four diets containing 40 g soyabean oil (SBO)/kg (low-fat diet), 150 g SBO/kg (SBO diet), 40 g SBO+110 g PHFO/kg (PHFO diet) or 40 g SBO+110 g THFO/kg (THFO diet) for 4 weeks. A lower absorption coefficient of the fat content was found in the THFO group (61 %) compared with the other groups (PHFO 95 %, SBO 99 %, low fat 98 %; P<0·05), which was mainly due to reduced absorption of VLCSFA. A reduced weight gain was found for the THFO group compared with the other groups, but this was only significant when compared with the SBO group (P<0·05). Faecal fat excretion (dry weight) was markedly increased in the THFO group (47 %), which was 2·4, 4·8 and 8·3 times higher compared with the groups fed PHFO, SBO and low-fat diets (P<0·05), respectively. Serum total cholesterol was reduced for the PHFO and THFO groups (P<0·05), whereas serum triacylglycerol was increased for the PHFO group compared with the other groups (P<0·05). Animals fed THFO diet had an increased content of 20:0 and 22:0 in the serum triacylglycerol fraction (P<0·05), whereas only 20:0 was increased in the serum phospholipid fraction (P<0·05). The low absorption coefficient of THFO must be considered if this fat is to be used for consumption by animals or man.