Variability of the conversion of β-carotene to vitamin A in women measured by using a double-tracer study design

• Published in: The American journal of clinical nutrition 2000-06, Vol.71 (6), p.1545-1554
• Main Authors: YUMEI LIN, DUEKER, S. R, BURRI, B. J, NEIDLINGER, T. R, CLIFFORD, A. J
• Format: Article
• Language: English
• Subjects: Absorption; Adult; beta Carotene - administration & dosage; beta Carotene - blood; beta Carotene - pharmacokinetics; Biological and medical sciences; Biological Availability; Deuterium; Enzymes. Coenzymes. Vitamins. Pigments; Female; Fundamental and applied biological sciences. Psychology; Humans; Isotopes; Kinetics; Medical research; Metabolism; Metabolisms and neurohumoral controls; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vitamin A; Vitamin A - analogs & derivatives; Vitamin A - blood; Women
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/71.6.1545

Blood beta-carotene and vitamin A responses to oral beta-carotene are variable in humans. Some individuals are characterized as responders and others as low- or nonresponders. A better understanding of the conditions that produce the variability is important to help design public health programs that ensure vitamin A sufficiency. Our objective was to assess variability in absorption and conversion of beta-carotene to vitamin A in vivo in humans by using a novel double-tracer ¿hexadeuterated (D(6)) beta-carotene and D(6) retinyl acetate approach. Eleven healthy women were housed at the US Department of Agriculture Western Human Nutrition Research Center metabolic unit for 44 d, where they consumed diets adequate in vitamins and minerals except for carotenoids. After an adaptation period, the women were given 30 micromol D(6) retinyl acetate orally, followed 1 wk later with 37 micromol D(6) beta-carotene (approximately equimolar doses). Time-dependent plasma concentration curves were determined for D(6) retinol, D(6) beta-carotene, and trideuterated (D(3)) retinol (derived from D(6) beta-carotene). Mean (+/-SE) absorption of D(6) beta-carotene was 3.3 +/- 1.3% for all subjects. The mean conversion ratio was 0.81 +/- 0.34 mol D(3) retinol to 1 mol D(6) beta-carotene for all subjects. However, only 6 of the 11 subjects had plasma D(6) beta-carotene and D(3) retinol concentrations that we could measure. The mean absorption of D(6) beta-carotene in these 6 subjects was 6.1 +/- 0.02% and their conversion ratio was 1.47 +/- 0.49 mol D(3) retinol to 1 mol D(6) beta-carotene. The remaining 5 subjects were low responders with