Increases in plasma holotranscobalamin can be used to assess vitamin B-12 absorption in individuals with low plasma vitamin B-12.
Low plasma concentrations of vitamin B-12 are common in Indians, possibly due to low dietary intakes of animal-source foods. Whether malabsorption of the vitamin contributes to this has not been investigated. A rise in the plasma holotranscobalamin (holo-TC) concentration after a standard dose of oral vitamin B-12 has been proposed as a measure of gastrointestinal absorption in people with normal plasma vitamin B-12 concentrations. We studied 313 individuals (children and parents, 109 families) in the Pune Maternal Nutrition Study. They received 3 doses of 10 microg (n = 191) or 2 microg (n = 122) of cyanocobalamin at 6-h intervals. A rise in plasma holo-TC of > or =15% and >15 pmol/L above baseline was considered normal vitamin B-12 absorption. The baseline plasma vitamin B-12 concentration was <150 pmol/L in 48% of participants; holo-TC was <35 pmol/L in 98% and total homocysteine was high in 50% of participants (>10 micromol/L in children and >15 micromol/L in adults). In the 10 microg group, the plasma holo-TC concentration increased by 4.8-fold from (mean +/- SD) 9.3 +/- 7.0 pmol/L to 53.8 +/- 25.9 pmol/L and in the 2 microg group by 2.2-fold from 11.1 +/- 8.5 pmol/L to 35.7 +/- 19.3 pmol/L. Only 10% of the participants, mostly fathers, had an increase less than the suggested cut-points. Our results suggest that an increase in plasma holo-TC may be used to assess vitamin B-12 absorption in individuals with low vitamin B-12 status. Because malabsorption is unlikely to be a major reason for the low plasma vitamin B-12 concentrations in this population, increasing dietary vitamin B-12 should improve their status.
Kamalnayan Bajaj Diabetology Research Centre, King Edward Memorial Hospital Research Centre, Pune, India.
Dattatray S
DS
Bhat
Nileema V
NV
Thuse
Himangi G
HG
Lubree
Charudatta V
CV
Joglekar
Sadanand S
SS
Naik
Lalita V
LV
Ramdas
Carole
C
Johnston
Helga
H
Refsum
Caroline H
CH
Fall
Chittaranjan S
CS
Yajnik
D000328:Adult; D001827:Body Height; D001835:Body Weight; D002318:Cardiovascular Diseases / Q000453:epidemiology; D002648:Child; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology; D005220:Fathers; D005260:Female; D005492:Folic Acid / Q000097:blood; D006454:Hemoglobins / Q000378:metabolism; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D039382:Maternal Nutritional Physiological Phenomena; D009034:Mother-Child Relations; D014155:Transcobalamins / Q000378:metabolism*; D014805:Vitamin B 12 / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D014806:Vitamin B 12 Deficiency / Q000097:blood / Q000175:diagnosis*
D006454:Hemoglobins; D014155:Transcobalamins; D006710:Homocysteine; D005492:Folic Acid; D014805:Vitamin B 12