In that paper at least, the peanut oil was just used as an inert vehicle or adjuvant for the molecules being studied (cholesterol and methionine). See Materials

In that paper at least, the peanut oil was just used as an inert vehicle or adjuvant for the molecules being studied (cholesterol and methionine). See Materials & Methods: "The peanut oil aids in the absorption of cholesterol as well as providing extra fat to the diet to resemble human diet, and it does not affect aortic pathology or endothelial function (Zulli et al. 2003)."