Failure of Enzymic Cleavage of β-Carotene

Abstract

A 10-year-old Lebanese Arab girl had vitamin A deficiency as evidenced by night blindness, bilateral Bitot's spots, and very low plasma vitamin A concentration (7\g=m\g/ 100 ml). Total plasma carotenoid values were high with about 50% as \g=b\-carotene. Repeated blood sampling after large doses of \g=b\-carotene failed to produce any retinyl ester in the plasma whereas there was significant rise of ester levels in three control subjects. Preformed vitamin A cured the clinical condition and caused retinyl ester to appear in the plasma. There was no malabsorption, hypothyroidism, or liver dysfunction. The evidence suggests failure of enzymic conversion of \g=b\-carotene to retinal in the intestine as the cause of vitamin A deficiency.

SNP rs6564851 in the BCO1 Gene Is Associated with Varying Provitamin a Plasma Concentrations but Not with Retinol Concentrations among Adolescents from Rural Ghana

“…To date, only a few studies have described the same phenomenon that we observed in the Agogo 2000 birth cohort study [46,47]. Genetic variants have previously contributed to the interindividual variability of plasma carotenoids, mainly in non-African populations [20].…”

Human Bioavailability of Vitamins

“…Low protein diets reduced dioxygenase activity in rats (Gronowska-Senger & Wolf, 1970). Failure to split 8-carotene in man is rare but can lead to metabolic carotenaemia at low intakes of carotenoids (Monk, 1982) or to vitamin A deficiency if retinol intake is low (McLaren & Zekian, 1971).…”