Comparative in vivo study on the digestion behaviors of three typical saturated dietary fats in Sprague Dawley rats

The intake of saturated fats could result in increased risks of metabolic disorders, which are closely related to the digestion behaviors of these fats. However, the specific differences and satiety signal regulation of different saturated fats during gastrointestinal digestion are still unknown. Therefore, a comparative study was conducted to investigate the digestion behaviors of three typical saturated dietary fats (i.e. coconut oil, CO; lard fat, LO; palm oil, PO) using Sprague Dawley (SD) rats. This study suggested that the rate and degree of digestion were as follows: CO ≈ LO > PO. In the distal ileum section, more unabsorbed free fatty acids (FFAs) were observed in the CO and LO group, while more undecomposed triglycerides (TAGs) were found in the PO group. In particular, after 4 h of digestion in the gastrointestinal tract, the CO and LO groups accumulated 17.97 % and 19.95 % of FFAs, respectively, while the PO group had only 5.61 % of FFAs. Meanwhile, the TAG content in the PO group was 4.42 %, compared to 3.24 % and 2.44 % in the CO and LO groups, respectively. Furthermore, PO oral gavage administration resulted in higher gastric emptying and intestinal transit rates, thereby upregulating levels of satiety-signaling hormones and affecting the digestion rate. These results indicated that saturated fats rich in short- and medium-chain saturated fatty acids (SCFAs and MCFAs), or those with a greater variety and crystalline types of TAGs, are more readily broken down. Moreover, the secretion of satiety-signaling hormones during digestion significantly influences the digestion rate of saturated fats. This study provides insights into the possible mechanisms underlying differences in the digestion rates of typical dietary saturated fats, which could lay the theoretical foundation for balanced dietary fat consumption.