Assessment of the intestinal retention of beta-carotene in humans

Assessment of the intestinal absorption of beta-carotene (BC) in humans as well as plasma clearance of BC has been difficult. We have used the total gut washout method (TGWM) to assess BC retention during transit through the intestine, as well as the effect that different diets and age have on BC retention.

HPLC was used to quantitate fecal and serum BC concentrations from young and elderly subjects who had undergone the TGWM to remove all intestinal contents prior to ingesting BC or placebo with or without a meal. Meals contained different combinations of calories and fat.

In subjects receiving no meal, 83% of ingested BC was recovered in rectal effluent collected within 24 hours post-BC administration. The quantity of BC in feces of individuals receiving meals was 49-71%. There was no significant change in serum concentrations of other carotenoids or retinoids following consumption of BC with any of the different meals. Interestingly, both diet and age influenced the efficiency of BC absorption. An increase in dietary fat content resulted in an higher serum BC concentration in young subjects within 8 and at 24 hours post BC administration, whereas a higher caloric content resulted in a decrease in serum BC concentration in older subjects within 8 hours of BC administration.

Results indicate that the TGWM provides an accurate means for assessing the intestinal retention of BC in humans.