Processing of vitamin A and E in the human gastrointestinal tract

We aimed to provide basic data on the processing of vitamin A and E in the human gastrointestinal tract and to assess whether the size of emulsion fat globules affects the bioavailability of these vitamins. Eight healthy men received intragastrically two lipid formulas differing in their fat-globule median diameter (0.7 vs. 10.1 mum). Formulas provided 28 mg vitamin A as r etinyl palmitate and 440 mg vitamin E as all-rac alpha -tocopherol. Vitamin s were measured in gastric and duodenal aspirates, as well as in chylomicro ns, during the postprandial period. The gastric emptying rate of lipids and vitamin A and E was similar. The free retinol/total vitamin A ratio was no t significantly modified in the stomach, whereas it was dramatically increa sed in the duodenum. The proportion of ingested lipid and vitamins was very similar in the duodenal content. The chylomicron response of lipids and vi tamins was not significantly different between the two emulsions. Our main conclusions are as follows: 1) there is no significant metabolism of vitami n A and E in the human stomach, 2) the enzyme(s) present in the duodenal lu men is significantly involved in the hydrolysis of retinyl esters, and 3) t he size of emulsion fat globules has no major effect on the overall absorpt ion of vitamin A and E.