Vitamin D status among 4-month-old infants in New England: a prospective cohort study

Concerns over vitamin D deficiency in infants and children recently prompted the American Academy of Pediatrics to recommend increased supplementation. Few studies have examined vitamin D status in the same infants over time. Also, while many researchers label "breastfeeding" as a risk factor for vitamin D deficiency, few differentiate between any breastfeeding, exclusive breastfeeding, and supplemented or unsupplemented breastfeeders.

To determine predictors of 25(OH)D deficiency at 4 months in a group of children previously tested at birth.

We enrolled newborns from 2005 to 2007 at an urban Boston hospital. Maternal and infant blood samples were collected within 72 hours of birth. At 4 months, we obtained a second infant blood sample.

At 4 months, 11.9% of the 177 infants were vitamin D deficient compared to 37.5% at birth (25(OH)D <20 ng/mL). Median 25(OH)D was 35.2 ng/mL (range, 5-100.8; 95% confidence interval [CI], 32.8-37.6). At 4 months, 40% of unsupplemented infants were deficient. Lack of supplementation was significantly associated with increased risk of deficiency (adjusted odds ratio [AOR], 19.3; 95% CI, 4.80-77.2). Being outside at least 10 minutes a day, once per week, was protective (AOR, 0.12; 95% CI, 0.02-0.66), as was increasing gestational age (AOR, 0.36; 95% CI, 0.19-0.69). In 48.4% of patients, physicians failed to prescribe vitamin D at 2 months.

Despite inconsistent supplementation, a smaller proportion of infants were vitamin D deficient at 4 months than at birth. While supplemented breastfed infants were not at risk of deficiency, unsupplemented exclusively breastfed infants were at high risk of severe deficiency.