Retinol lipid digestion

This could include retinol, cholecalciferol/ergocalciferol, a-tocopherol, vitamin K from food, all of which are more readily absorbed when they can be part of a normal mixed micelle process that occurs with lipid digestion and absorption... 

Dietary retinyl esters, retinol, and provitamin A carotenoids are dispersed and emulsified in the stomach during the gastric phase of lipid digestion. They then enter the lumen of the duodenum where extensive hydrolysis of retinyl esters takes place. In infants, the bile salt-stimulated lipase in human milk may play a role in retinyl ester hydrolysis in the duodenum (Fredrikzon et al., 1978). The major retinyl ester hydrolase activity that acts in the intestines is, however, derived from the pancreas. 

Dietary retinyl esters must be hydrolyzed in the lumen of the small intestine before retinol is absorbed, while carotenoids must be absorbed into the intestinal mucosa before being cleaved intracel-lularly. Several enzymes with retinyl ester hydrolase (REH) activity are present in pancreatic juice or on the brush border of duodenal and jujenal enterocytes (Figure 3). Retinol and carotenoids must be solubilized in the lumen in mixed micelles composed of bile acids and products of lipid digestion prior to their uptake into enterocytes. These processes require the release of an adequate amount of bile... 

D. Because cystic fibrosis leads to pancreatic damage and diminution of the abihty to secrete HCO3 and pancreatic digestive enzymes with the result that fat and protein are absorbed poorly. Retinol is a fat-soluble vitamin that must be absorbed along with lipid micelles other fat-soluble vitamins are E, D, and K. The other vitamins hsted are water-soluble and their absorption is not significantly affected. 

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