Vitamin D, race, and risk for anemia in children

Objective To examine the association between 25-hydroxyvitamin D [25(OH)D] deficiency and anemia in a cohort of otherwise-healthy children and to determine whether race modifies the association between 25(OH)D status and hemoglobin (Hgb). Study design Cross-sectional study of 10 410 children and adolescents ages 1-21 years from the 2001-2006 National Health and Nutrition Examination Survey. Anemia was defined as Hgb less than the 5th percentile for age and sex based on National Health and Nutrition Examination Survey III (1988-1994) data. Results Lower 25(OH)D levels were associated with increased risk for anemia; <30 ng/mL, adjusted OR 1.93, 95% CI 1.21-3.08, P =.006, and <20 ng/mL, OR 1.47, 95% CI 1.14-1.89, P =.004. In linear regression, small but significant increases in Hgb were noted in the upper quartiles of 25(OH)D compared with the lowest quartile (<20 ng/mL) in the full cohort. Results of race-stratified linear regression by 25(OH)D quartile in white children were similar to those observed in the full cohort, but in black children, an increase in Hgb in the upper 25(OH)D quartiles was only apparent compared with the lowest black race-specific quartile (<12 ng/mL). Conclusion 25(OH)D deficiency is associated with increased risk of anemia in healthy US children, but the 25(OH)D threshold levels for lower Hgb are lower in black children in comparison with white children.