Vitamin B(12) status in children with cystic fibrosis and pancreatic insufficiency.

OBJECTIVES

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 years) and categorized as elevated (serum B12 above reference range for age and sex [Hi-B12]) or within reference range (serum B12 within reference range for age and sex) for age and sex. Serum homocysteine, plasma B6, red blood cell folate, height, weight, and body mass index z scores, pulmonary function, energy, and dietary and supplement-based vitamin intake were assessed.

RESULTS

A total of 106 subjects, mean age 10.4 ± 3.0 years, participated in the study. Median serum B12 was 1083 pg/mL, with 56% in the Hi-B12 group. Dietary and supplement-based B12 intakes were both high representing 376% and 667% recommended dietary allowance (RDA), respectively. The Hi-B12 group had significantly greater supplement-based B12 intake than the serum B12 within reference range for age and sex group (1000% vs 583% RDA, P < 0.001). Multiple logistic regression analysis showed that high supplement-based B12 intake and age >12 years increased the risk of Hi-B12, whereas higher forced expiratory volume at 1 second (FEV1) decreased the risk (pseudo-R = 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 forced expiratory volume at 1 second.