Prescribing higher doses of vitamin D may not provide any additional benefits to children’s brain development, a new study suggests.
New research published online in JAMA found that there were no differences in children’s developmental milestones or social-emotional problems when given a higher daily dose of 1,200 IU of vitamin D versus the standard dose of 400 IU.
Although past studies have looked into the relationship between vitamin D and neurodevelopment in children, the findings were inconsistent. A 2019 study published in Psychoneuroendocrinology found that vitamin D deficiency could be a biological risk factor for psychiatric disorders and that vitamin D acts as a neurosteroid with direct effect on brain development. However, a 2021 study published in Global Pediatric Health found no significant association between vitamin D levels and neurodevelopmental status in children at 2 years old.
Researchers of the current study said they expected to find a positive association between higher vitamin D levels and neurodevelopment.
“Our results highlight that the current recommendations, set forth mainly on the basis of bone health, also support healthy brain development,” said study author Kati Heinonen, PhD, associate professor of psychology and welfare sciences at Tampere (Finland) University. “Our results also point out that higher than currently recommended levels do not add to the benefits received from the vitamin D supplements.”
For the study, Dr. Heinonen and colleagues analyzed data from a double-blind, randomized clinical trial involving healthy infants born full-term between Jan. 1, 2013, and June 30, 2014, at a maternity hospital in Helsinki. They got follow-up information on 404 infants who were randomized to receive 400 IU of oral vitamin D supplements daily and 397 infants who received 1,200 IU of vitamin D supplements from 2 weeks to 24 months of age.
Researchers found no differences between the 400-IU group and the 1,200-IU group in the mean adjusted Ages and Stages Questionnaire total score at 12 months, a questionnaire that’s used to measure communication, problem solving, gross motor skills, fine motor skills, and personal and social skills. However, they did find that children receiving 1,200 IU of vitamin D supplementation had better developmental milestone scores in communication and problem-solving skills at 12 months.
Furthermore, they also found that higher vitamin D concentrations were associated with fewer sleeping problems at 24 months.
The researcher’s findings did not surprise Francis E. Rushton Jr., MD, a clinical professor of pediatrics at the University of South Carolina, Columbia, who was not involved in the study. “This study reveals that more is not always better,” Dr. Rushton said in an interview.
Dr. Rushton, who is also the medical director of the Quality Through Innovation in Pediatrics network, said other ways to enhance early brain development include initiatives like infant home visitation and language enrichment programs like Reach Out and Read.
Dr. Heinonen noted that the study’s findings might be different if it had been conducted on infants from a different country.
“We have to remember that the participants were from northern European countries where several food products are also fortified by vitamin D,” Dr. Heinonen explained. “Thus, direct recommendations of the amount of the supplementation given for children from 2 weeks to 2 years in other countries should not be done on the basis of our study.”
Researchers also observed that the children receiving 1,200 IU of vitamin D supplementation had a risk of scoring higher on the externalizing symptoms scale at 24 months, meaning these infants are more likely to lose their temper and become physically aggressive.
“We could not fully exclude potential disadvantageous effects of higher doses. Even if minimal, the potential nonbeneficial effects of higher than standard doses warrant further studies,” she said.
Researchers said more studies are needed that follow children up to school age and adolescence, when higher cognitive abilities develop, to understand the long-term outcomes of early vitamin D supplementation.