Preventing vitamin B12 deficiency in South Asian women of childbearing age: a randomised controlled trial comparing an oral vitamin B12 supplement with B12 dietary advice.

BACKGROUND/OBJECTIVES: To examine the effectiveness, acceptability and sustainability of interventions to reduce vitamin B12 (B12) deficiency in South Asian women before conception.

SUBJECTS/METHODS: A 6-month randomised controlled trial conducted in Auckland, New Zealand. Participants (62 South Asian women, 18-50 years old) were stratified by dietary practices, then randomised to three treatment groups: B12 Supplement (oral cyanocobalamin 6 μg/day) (n=21), Placebo (n=21), or B12 Dietary Advice (n=20). Primary outcome measures were changes in B12 biomarkers (serum B12 and holotranscobalamin (holoTC)) at 6 months. Dietary B12 intake was estimated from a B12 food-specific frequency questionnaire (B12FFQ). Intention-to-treat analysis was applied using 'last observation carried forward' method. Changes in B12 biomarkers by treatment were compared using analysis of variance. Pearson's correlations tested relationships between dietary B12 intake and B12 biomarkers.

RESULTS: At baseline, 48% of women tested as insufficient or deficient in serum B12 (<222 pmol/l) and 51% as insufficient or deficient in holoTC (<45 pmol/l). B12 status was moderately correlated with dietary B12 intake (r=0.5, 95% confidence interval (CI) (0.3-0.7)) and 44% of women reported insufficient dietary intake (<2.4 μg/day). B12 Supplement was the only treatment group to record a significant increase in B12 biomarkers over 6 months: serum B12 by 30% (95% CI (11-48%)) and holoTC by 42% (12-72%).

CONCLUSIONS: The prevalence of B12 insufficiency among Auckland South Asian women is high and moderately correlated with inadequate intake of foods that contain B12. Cyanocobalamin supplementation (6 μg/day) was associated with improved B12 biomarkers, with a potential to improve preconception B12 status in South Asian women.