Vitamin D Deficiency Is Not Associated With Growth or the Incidence of Common Morbidities Among Tanzanian Infants

Abstract

Objective: The objective of this study was to examine risk factors for vitamin D deficiency and determine the association of vitamin D status with child growth and incidence of common morbidities among Tanzanian infants.

Methods: A prospective cohort of 581 Tanzanian infants born to human immunodeficiency virus (HIV)-uninfected mothers had serum 25-hydroxyvitamin D assessed at 6 weeks and 6 months of age. Infants were seen at monthly clinic visits for growth monitoring until 18 months of age. Physicians examined infants every 3 months or when an illness was noted to document morbidities.

Results: The prevalence of vitamin D deficiency (<20 ng/mL) declined from 76.4% at 6 weeks of age to 21.2% at 6 months. Infants who were exclusively breastfed at 6 weeks of age had 2.05 (95% confidence interval 1.11-3.79; P = 0.02) times the risk of vitamin D deficiency as compared formula-fed infants. After multivariate adjustment, there was no association of vitamin D status at 6 weeks or 6 months with the incidence of stunting, wasting, or underweight. There was also no association of low vitamin D with the incidence of diarrhea, upper respiratory infection, acute lower respiratory tract infection, or malaria.

Conclusions: Vitamin D deficiency is common during early infancy, particularly among exclusively breastfed infants; however, these observational data suggest it may not be an important contributor to morbidity and growth among the general population of Tanzanian infants. Future studies of vitamin D among high-risk infants, including those with low birthweight and exposed to HIV, may be warranted.

FIGURE 1

Distribution of 25(OH)D concentration (ng/mL) at 6 weeks (panel A) and 6 months (panel B) of age among 581 infants. 25(OH)D = 25-hydroxyvitamin D.

FIGURE 2

Mean length-for-age z score (LAZ) (panel A), weight-for-length z score (WLZ) (panel B), and weight-for-age z score (WAZ) (panel C) growth curves stratified by 6-week 25(OH)D concentration. There was no significant difference in trajectory of LAZ or WAZ by 6-week vitamin D status categories (P values for difference in trajectory >0.05). There was a significant difference in WLZ trajectory for infants with 25(OH)D concentrations at 6 weeks of >20 ng/mL as compared with infants with concentrations 10–20 ng/mL (P value for difference in WLZ trajectory <0.01). 25(OH)D = 25-hydroxyvitamin D.

FIGURE 3

Mean length-for-age z score (LAZ) (panel A), weight-for-length z score (WLZ) (panel B), and weight-for-age z score (WAZ) (panel C) growth curves stratified by 6 month 25(OH)D concentration. There was no significant difference in trajectory of LAZ, WLZ, or WAZ by 6-month vitamin D status categories (P values for difference in trajectory >0.05). 25(OH)D = 25-hydroxyvitamin D.