Wednesday, May 15, 2013
Subjects included 96 infants born between 28 and 34 weeks' gestation who were
receiving milk feeding. Blood samples were taken from the infants to determine
their serum vitamin D levels. The infants then were randomly assigned to receive
either 800 IU or 400 IU of oral vitamin D3. Neither the parents nor the primary
investigator was aware of which dose the infants were receiving.
Researchers compared whether the prevalence of vitamin D insufficiency (VDI) at
40 weeks and at 3 months corrected age differed between the groups. They also
looked at whether infants with higher vitamin D levels also had stronger bones
at 3 months corrected age and whether supplementation led to vitamin D levels
that were too high. Results showed that VDI was common in both groups before
they received supplements (79 percent of the 800 IU group and 83 percent of the
400 IU group).
After supplementation, the prevalence of VDI at 40 weeks was 43 percent lower in
the 800 IU group than the 400 IU group (38 percent vs. 67 percent). In addition,
VDI was significantly lower in the 800 IU group when the infants were 3 months
old (12 percent vs. 35 percent). Four infants needed to be supplemented with 800
IU daily to reduce one case of vitamin D insufficiency, said lead author Chandra
Kumar Natarajan, DM. "The study results show conclusively that in preterm
infants with high rates of vitamin D insufficiency at baseline, supplementation
with 800 IU of vitamin D3 per day compared to 400 IU per day reduces vitamin D
insufficiency at term equivalent age and at 3 months," Dr. Natarajan said.
"There also is a trend toward a decrease in the prevalence of vitamin D
insufficiency even in the 400 IU group at 3 months. Therefore, 400 IU per day
may be sufficient after 3 months."
Despite significant improvement in serum vitamin D levels in the 800 IU group,
higher levels did not result in better bone mineralisation at 3 months of age –
as measured by dual energy X-ray absorptiometry (DEXA). In addition, weight,
length and head circumference did not differ significantly between the groups.
Dr. Natarajan also noted that one infant in the 800 IU group had vitamin D
levels that were higher than recommended levels at 3 months of age, despite the
levels at term age being normal. Excess vitamin D for at least one month can
cause decreased muscle tone, decreased appetite, irritability and constipation,
among other problems. The infant did not experience any major effects.
"The incidence of vitamin D excess in the 800 IU group may indicate the need for
monitoring vitamin D levels in infants on vitamin D supplementation, but we need
larger studies to answer this," he said. "Similarly, larger studies with longer
duration of follow-up may be needed to find out any meaningful difference in
clinical outcomes such as bone mineralisation."