The Intraluminal Phase of Fat Digestion in Man: The Lipid Content of the Micellar and Oil Phases of Intestinal Content Obtained during Fat Digestion and Absorption*

For nearly a century, it has been known that dietary triglyceride is hydrolyzed in the small in- testinal lumen by pancreatic lipase.Early work- ers had shown the presence of fatty acid (believed to be largely present as paraffin chain soap) in intestinal content after the ingestion of fat.At the turn of the century, the field of fat ab- sorption was dominated by Pfliiger, who staunchly defended the view that fat was largely hydrolyzed to fatty acid and that absorption could only be in the form of fatty acid and paraffin chain soap (3).The observation that paraffin chain soap was insoluble at the rather acid pH of intestinal content was disturbing, but seemed of little im- portance after Verzar and McDougall demonstrated the considerable solubility of fatty acids in bile salt solutions at a pH corresponding to that present in intestinal content (4).In 1935, however, Artom and Reale (5) demonstrated that monoglycerides and diglycerides could be isolated after triglyceride was hydrolyzed by pancreatic lipase in vitro.Their presence in in- testinal content was established by Frazer and Sammons in 1945 (6).Frazer, Schulman, and Stewart (7) subse- quently noted that triolein forms a stable emul- sion in an aqueous mixture of bile salt, fatty acid,