Absorption of isomeric, palmitic acid-containing triacylglycerols resembling human milk fat in the adult rat

The effect of the positional distribution of palmitic acid (16∶0) in triacylglycerols (TAG) on 16∶0 apparent absorption in adult rats was investigated. The rats were fed two diets which contained 30 energy % as fat with identical total fatty acid compositions, both containing 30% 16∶0. The Betapol diet contained TAG with 73% of total 16∶0 in thesn-2 position, the control diet contained TAG with 6% of total 16∶0 in thesn-2 position. After six weeks on these diets, the rats were killed two or six hours after the last meal, and the small intestine was removed, cut into 10-cm segments, and the fatty acid composition of the segment's contents was determined. At both time points the amount of 16∶0 in the intestinal segments starting at 40 cm from the stomach was much lower in the animals fed Betapol than in the animals fed the control diet. Overall absorption of 16∶0 and stearic acid was significantly greater in the Betapol group. Absorption of oleic and linoleic acid from the small intestine was similar in both groups, although the overall absorption was significantly greater in the animals fed Betapol. Total fat absorption was significantly higher in the Betapol-fed rats than in the control-fed rats. No effect on calcium and nitrogen absorption, on plasma total cholesterol and TAG levels, and on bodyweights (growth) was seen. The data demonstrate that the positional distribution of the fatty acids in the TAG molecule affects the site of absorption in the small intestine and particularly the net absorption of saturated fatty acids.