Effect of mono- and diglycerides on the digestion and absorption of lutein in lymph fistula rats.

Breast milk lutein is better absorbed by infants than lutein delivered in infant formula. Therefore, we wanted to better understand the possible absorption differences of lutein in breast milk vs. that in infant formula by determining its bioavailability after gastric administration and whether the intestinal absorption of lutein can be improved by using new delivery vehicles. Study 1 compared the intestinal uptake,and the lymphatic and portal transport of lutein in conscious lymph fistula rats. Four groups of lymph- and portal vein-cannulated rats ( n = 8-10/group) were randomized to receive via gastric tube increasing doses (10, 20, 40, or 80 mg/kg) of 20% lutein in safflower oil (SO) suspension to assess whether there was a saturable level of lutein that could be absorbed and transported in lymph. Aliquots of hourly portal blood and lymph were taken for lutein and zeaxanthin analyses. The dose-response study showed that 20 mg/kg lutein was the saturable level of lymphatic lutein absorption with no lutein detected in portal circulation at any dosage level tested. Study 2 randomized five groups of lymph fistula rats ( n = 4-9/group) to receive 20 mg/kg lutein from either lutein in SO or lutein in four different mono- and diglyceride oils (MDGs). Gastric infusion of lutein suspended in MDG (20 mg/kg) significantly improved (71-211%, P < 0.05) lymphatic lutein output 2-6 h after lipid feeding vs. lutein in SO. Lymphatic zeaxanthin (10% of the lutein fed mixture) transport in both Study 1 and Study 2 followed that of lutein. We conclude that a mixture of MDGs helps solubilize lutein and facilitate gastrointestinal micelle formation, thus improving lymphatic lutein absorption compared with triglyceride oils. NEW & NOTEWORTHY This paper describes how lutein is digested and absorbed by the gastrointestinal tract by using the conscious lymph fistula rat model. Our dose-response study showed that absorption and lymphatic transport of lutein is a saturable process with no lutein detected in portal circulation at any dosage level tested. Our paper also provides insight into how this process can be improved by modifying the typical lipid mixtures carrying the lutein.