Objective
Unexpectedly high serum B12 concentrations were noted in most study subjects with cystic fibrosis (CF) and pancreatic insufficiency (PI) participating in a nutrition intervention at the baseline evaluation. The objectives of this study were to determine dietary, supplement-based and enzyme-based B12 intake, serum B12 concentrations, and predictors of vitamin B12 status in children with CF and PI.
Study Design
Serum B12 status was assessed in subjects (5-18 yrs) and categorized as elevated (Hi-B12) or within reference range (RR-B12) for age and sex. Serum homocysteine, plasma B6, red blood cell folate, height, weight, and body mass index Z scores, pulmonary function, energy, dietary and supplement-based vitamin intake were assessed.
Results
106 subjects, mean age 10.4 ± 3.0 years participated. Median serum B12 was 1083 pg/ml, with 56% in the Hi-B12 group. Dietary and supplement-based B12 intake were both high representing 376% and 667% Recommended Dietary Allowance (RDA). The Hi-B12 group had significantly greater supplement-based B12 intake than the RR-B12 group (1000 vs. 583% RDA, p<0.001). By multiple logistic regression analysis, high supplement-based B12 intake and age >12 years increased risk for Hi-B12, while higher FEV1 decreased risk (Pseudo-R2=0.18, P<0.001).
Conclusions
Serum B12 was elevated in the majority of children with CF and PI. Supplement-based B12 intake was 6 to 10 times the RDA, and strongly predicted elevated serum B12 status. The health consequences of lifelong high supplement-based B12 intake and high serum B12 are unknown and require further study, as does the inversed correlation between serum B12 and FEV1.