Higher-dose vitamin D in infancy linked to better emotional wellbeing years later

A Finnish doctoral study suggests vitamin D supplementation during the first two years of life may be associated with fewer anxiety and low-mood symptoms and healthier neurocognitive development in later childhood.

A Finnish doctoral dissertation suggests that vitamin D may do more than support bone health in early life, with findings pointing to possible links between supplementation in infancy, better long-term emotional wellbeing and healthier neurocognitive development. The work, reported by Iltalehti, draws on two large Finnish research cohorts and adds to a growing body of evidence that the vitamin’s role in child development may be broader than once thought.

The research was based on the VIDI infant trial and the PREDO pregnancy follow-up study, both conducted in Finland. In the VIDI study, 987 healthy full-term infants were randomly assigned to receive either 400 IU or 1,200 IU of vitamin D3 daily for the first two years of life. The Helsinki study description says the trial was double-blind and ran between 2013 and 2014, with earlier results showing that the higher dose improved bone strength and reduced parent-reported infections in early childhood.

In the newer follow-up, children were assessed again at ages six to eight, allowing researchers to look beyond immediate physical outcomes. According to the materials summarising the dissertation, vitamin D levels were measured in mothers during pregnancy and in children at ages one and two, while parents also completed questionnaires about sleep. Later, psychologists used standard tests and parent reports to evaluate neurocognitive development. The pregnancy cohort also captured depressive symptoms in expectant mothers, giving the researchers a broader picture of family health and development.

The most striking takeaway is that higher vitamin D intake in the first two years of life may be associated with fewer later internalising problems, a term that covers symptoms such as anxiety and low mood. A separate study in JAMA Pediatrics previously reported benefits from the higher infant dose in the same Finnish trial, and another later paper found no harm in the higher supplementation strategy. Taken together, the Finnish work suggests that vitamin D in infancy is not only safe at the studied doses, but may also have measurable benefits for development that deserve further investigation.