Allen LH, Miller JW, de Groot L, Rosenberg IH, Smith AD, Refsum H, et al. Biomarkers of nutrition for development (BOND): Vitamin B-12 review. J Nutr. 2018;148:1995S–2027S.

Article 
PubMed 
PubMed Central 

Google Scholar
 

Magnúsdóttir S, Ravcheev D, de Crécy-Lagard V, Thiele I Systematic genome assessment of B-vitamin biosynthesis suggests co-operation among gut microbes. Front Genet. 2015;6:148.

Tarracchini C, Lugli GA, Mancabelli L, van Sinderen D, Turroni F, Ventura M. et al. Exploring the vitamin biosynthesis landscape of the human gut microbiota. Msystems 2024;9:e0092924.

Kurpad AV, Pasanna RM, Hegde SG, Patil M, Mukhopadhyay A, Sachdev HS, et al. Bioavailability and daily requirement of vitamin B12 in adult humans: an observational study of its colonic absorption and daily excretion as measured by [13C]-cyanocobalamin kinetics. Am J Clin Nutr. 2023;118:1214–23.

Article 
CAS 
PubMed 

Google Scholar
 

Yang Y, Ke Y, Liu X, Zhang Z, Zhang R, Tian F, et al. Navigating the B vitamins: Dietary diversity, microbial synthesis, and human health. Cell Host Microbe. 2024;32:12–18. https://doi.org/10.1016/j.chom.2023.12.004.

Article 
CAS 
PubMed 

Google Scholar
 

Carmel R. Malabsorption of food cobalamin. Baillieres Clin Haematol. 1995;8:639–55.

Article 
CAS 
PubMed 

Google Scholar
 

Nielsen MJ, Rasmussen MR, Andersen CB, Nexø E, Moestrup SK Vitamin B12 transport from food to the body’s cells—a sophisticated, multistep pathway. Nat Rev Gastroenterol Hepatol. 2012;9:345-54.

Schilling RF. The absorption and utilization of vitamin B12. Am J Clin Nutr. 1955;3:45–51.

Article 
CAS 
PubMed 

Google Scholar
 

Devi S, Pasanna RM, Shamshuddin Z, Bhat K, Sivadas A, Mandal AK, et al. Measuring vitamin B-12 bioavailability with [13C]-cyanocobalamin in humans. Am J Clin Nutr. 2020;112:1504–15.

Article 
PubMed 

Google Scholar
 

Bor MV, Çetin M, Aytaç S, Altay C, Nexo E. Nonradioactive vitamin B12 absorption test evaluated in controls and in patients with inherited malabsorption of vitamin B12. Clin Chem. 2005;51:2151–5.

Article 
CAS 
PubMed 

Google Scholar
 

Hvas AM, Morkbak AL, Nexo E. Plasma holotranscobalamin compared with plasma cobalamins for assessment of vitamin B12 absorption; optimisation of a non-radioactive vitamin B12 absorption test (CobaSorb). Clin Chim Acta. 2007;376:150–4.

Bor MV, Nexø E, Hvas AM. Holo-transcobalamin concentration and transcobalamin saturation reflect recent vitamin B12 absorption better than does serum vitamin B12. Clin Chem. 2004;50:1043–9.

Article 
CAS 
PubMed 

Google Scholar
 

Greibe E, Mahalle N, Bhide V, Heegaard CW, Naik S, Nexo E. Increase in circulating holotranscobalamin after oral administration of cyanocobalamin or hydroxocobalamin in healthy adults with low and normal cobalamin status. Eur J Nutr. 2018;57:2847–55. https://doi.org/10.1007/s00394-017-1553-5.

Article 
CAS 
PubMed 

Google Scholar
 

Hvas AM, Morkbak AL, Hardlei TF, Nexo E. The vitamin B12 absorption test, CobaSorb, identifies patients not requiring vitamin B12 injection therapy. Scand J Clin Lab Invest. 2011;71:432–8. https://doi.org/10.3109/00365513.2011.581389.

Article 
CAS 
PubMed 

Google Scholar
 

Yajnik C, Deshmukh U, Katre P, Limaye T Vitamin B12 deficiency in developing and newly industrialising countries. In: Vitamin B12- Advances and Insights. Edited by Rima Obeid. 1st ed. CRC Press; 2017.

Refsum H, Yajnik CS, Gadkari M, Schneede J, Vollset SE, Örning L, et al. Hyperhomocysteinemia and elevated methylmalonic acid indicate a high prevalence of cobalamin deficiency in Asian Indians. Am J Clin Nutr. 2001;74:233–41.

Article 
CAS 
PubMed 

Google Scholar
 

Yajnik CS, Deshpande SS, Lubree HG, Naik SS, Bhat DS, Uradey BS, et al. Vitamin B12 deficiency and hyperhomocysteinemia in rural and urban Indians. J Assoc Physicians India. 2006;54:775–82.

CAS 
PubMed 

Google Scholar
 

Yajnik CS, Deshpande SS, Jackson AA, Refsum H, Rao S, Fisher DJ, et al. Vitamin B12 and folate concentrations during pregnancy and insulin resistance in the offspring: the Pune Maternal Nutrition Study. Diabetologia. 2008;51:29–38.

Article 
CAS 
PubMed 

Google Scholar
 

Brito A, Habeych E, Silva-Zolezzi I, Galaffu N, Allen LH. Methods to assess vitamin B12 bioavailability and technologies to enhance its absorption. Nutr Rev. 2018;76:778–92. https://doi.org/10.1093/nutrit/nuy026.

Article 
PubMed 

Google Scholar
 

Sands T, Jawed A, Stevenson E, Smith M, Jawaid I. Guideline C. Vitamin B(12) deficiency: NICE guideline summary. BMJ. 2024;385:q1019. https://doi.org/10.1136/bmj.q1019.

Article 
PubMed 

Google Scholar
 

Bhat DS, Thuse NV, Lubree HG, Joglekar CV. Increases in plasma holotranscobalamin can be used to assess vitamin B12 absorption in individuals with low plasma vitamin B12. J Nutr. 2009;139:2119–23.

Article 
CAS 
PubMed 
PubMed Central 

Google Scholar
 

Deshmukh US, Joglekar CV, Lubree HG, Ramdas LV, Bhat DS, Naik SS, et al. Effect of physiological doses of oral vitamin B12 on plasma homocysteine: a randomized, placebo-controlled, double-blind trial in India. Eur J Clin Nutr. 2010;64:495–502.

Article 
CAS 
PubMed 
PubMed Central 

Google Scholar
 

Kelleher BP, Walshe KG, Scott JM, O’Broin SD. Microbiological assay for vitamin B12 with use of a colistin-sulfate-resistant organism. Clin Chem. 1987;33:52–54.

Article 
CAS 
PubMed 

Google Scholar
 

Kelleher BP, Broin SD. Microbiological assay for vitamin B12 performed in 96-well microtitre plates. J Clin Pathol. 1991;44:592–5.

Article 
CAS 
PubMed 
PubMed Central 

Google Scholar
 

Horne DW, Patterson D. Lactobacillus casei microbiological assay of folic acid derivatives in 96-well microtiter plates. Clin Chem. 1988;34:2357–9.

Article 
CAS 
PubMed 

Google Scholar
 

Tamura T, Freeberg LE, Cornwell PE. Inhibition by EDTA of growth of Lactobacillus casei in the folate microbiological assay and its reversal by added manganese or iron. Clin Chem. 1990;36:1993.

Article 
CAS 
PubMed 

Google Scholar
 

Ulleland M, Eilertsen I, Quadros EV, Rothenberg SP, Fedosov SN, Sundrehagen E, et al. Direct assay for cobalamin bound to transcobalamin (holo-transcobalamin) in serum. Clin Chem. 2002;48:526–32.

Article 
CAS 
PubMed 

Google Scholar
 

Refsum H, Johnston C, Guttormsen AB, Nexo E. Holotranscobalamin and total transcobalamin in human plasma: determination, determinants, and reference values in healthy adults. Clin Chem. 2006;52:129–37.

Article 
CAS 
PubMed 

Google Scholar
 

Shipchandler MT, Moore EG. Rapid, fully automated measurement of plasma homocyst(e)ine with the Abbott IMx analyzer. Clin Chem. 1995;41:991–4.

Article 
CAS 
PubMed 

Google Scholar
 

Verbeke GM, G. Linear Mixed Models for Longitudinal Data, Springer: New York, 2000.

Fedosov SN, Brito A, Miller JW, Green R, Allen LH Combined indicator of vitamin B12 status: modification for missing biomarkers and folate status and recommendations for revised cut-points. Clin Chem Lab Med. 2015;53:1215-25.

Hopewell S, Chan AW, Collins GS, Hróbjartsson A, Moher D, Schulz KF, et al. CONSORT 2025 explanation and elaboration: updated guideline for reporting randomised trials. BMJ. 2025;389:e081124. https://doi.org/10.1136/bmj-2024-081124.

Article 
PubMed 
PubMed Central 

Google Scholar
 

Sivadas A, Devi S, Pasanna RM, Dutta U, Sachdev HS, Kurpad AV. Novel genetic variants associated with stable isotope-based vitamin B(12) bioavailability measurements in healthy Indian adults. Am J Clin Nutr. 2025;122:1374–89. https://doi.org/10.1016/j.ajcnut.2025.08.005.

Article 
CAS 
PubMed 

Google Scholar