Holo-transcobalamin is an indicator of vitamin B-12 absorption in healthy adults with adequate vitamin B-12 status

• Published in: The American journal of clinical nutrition Vol. 85; no. 4; pp. 1057 - 1061
• Main Authors: von Castel-Roberts, Kristina M, Morkbak, Anne Louise, Nexo, Ebba, Edgemon, Claire A, Maneval, David R, Shuster, Jonathan J, Valentine, John F, Kauwell, Gail PA, Bailey, Lynn B
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Nutrition 01.04.2007; American Society for Clinical Nutrition
• Subjects: Absorption; Administration, Oral; Adolescent; Adult; adults; Area Under Curve; Biological and medical sciences; Biomarkers - blood; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; holo-transcobalamin; human nutrition; Humans; intestinal absorption; Male; men; Middle Aged; nutrient uptake; nutritional adequacy; Nutritional Status; Time Factors; transcobalamins; Transcobalamins - analysis; Transcobalamins - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vitamin B 12 - administration & dosage; Vitamin B 12 - blood; Vitamin B 12 - metabolism; Vitamin B 12 - pharmacokinetics; Vitamin B Complex - administration & dosage; Vitamin B Complex - blood; Vitamin B Complex - metabolism; Vitamin B Complex - pharmacokinetics; vitamin B12; vitamin supplements; women; Human; healthy adults; holo-transcobalamin; vitamin B-12 absorption; Absorption; vitamin B-12; holo- TC; Adult; Transcobalamin; B-Vitamins
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/85.4.1057

BACKGROUND:It has been hypothesized that the response of holo-transcobalamin (holo-TC) to oral vitamin B-12 may be used to assess absorption. To develop a reliable clinical absorption test that uses holo-TC, it is necessary to determine the optimal timeline for vitamin B-12 administration and postdose assessment. OBJECTIVE:The objective of this study was to assess the magnitude and patterns of change in the postabsorption response of holo-TC to oral vitamin B-12. DESIGN:Adult (18-49 y) male and female participants (n = 21) with normal vitamin B-12 status were given three 9-μg doses of vitamin B-12 at 6-h intervals beginning early morning (baseline) on day 1. Blood was drawn at 17 timed intervals over the course of 3 d for the analysis of holo-TC and other indicators of vitamin B-12 status. RESULTS:Mean holo-TC increased significantly (P < 0.001) from baseline at 6 h (11%) and 24 h (50%). TC saturation increased significantly (P < 0.001) from baseline at 12.5 h (33%) and 24 h (50%). The mean cobalamin concentration changed significantly (P < 0.001) from baseline at 24 h (15%) and 48 h (14%). The ratio of holo-TC to cobalamin increased significantly (P < 0.001) at 24 h (32%). CONCLUSIONS:The greatest increase in holo-TC was observed 24 h after ingestion of three 9-μg doses of vitamin B-12. Our results indicate that a vitamin B-12 absorption test based on measurement of holo-TC after administration of three 9-μg doses of vitamin B-12 should run for 24 h.