Vitamin D is already part of many prenatal conversations, usually because of its role in bone health and fetal development. But a new study raises a bigger question: could vitamin D during pregnancy also be linked to how children perform on some memory tests years later?
In a follow-up analysis of a Danish clinical trial, researchers found that children whose mothers received a higher dose of vitamin D3 during pregnancy scored better on some memory tests at age 10 than children whose mothers received the standard dose. The findings were published in JAMA Network Open.
That does not mean pregnant people should start taking more vitamin D on their own. The study is promising, but it is also the kind of research that needs careful interpretation.
The research came from the Copenhagen Prospective Studies on Asthma in Childhood 2010 cohort, which began following mothers and children more than a decade ago. During pregnancy, women were randomly assigned to receive either 2,800 international units (IU) of vitamin D3 per day or the standard Danish dose of 400 IU per day. The supplementation began at week 24 of pregnancy and continued until one week after birth.
When the children were about 10 years old, 498 of them completed a series of cognitive tests. These tests looked at areas such as memory, attention, problem-solving, processing speed and the ability to shift from one task or rule to another.
Children in the higher-dose vitamin D group performed better on tests of verbal memory and visual memory. In plain terms, that means they did better on tasks involving remembered words and remembered images or patterns.
Researchers also saw a possible benefit in a skill known as cognitive flexibility, which helps people adjust when instructions change or when they need to switch between tasks. But that finding became less certain after the researchers applied a statistical check meant to reduce the chance of false alarms.
That distinction matters. When a study measures many outcomes, some results can look meaningful by chance. The memory findings were stronger, while the cognitive flexibility result should be viewed more cautiously.
The study has several strengths. It followed children for 10 years, came from a randomized trial and used direct cognitive testing rather than relying only on parent reports.
Still, there are limits. The original trial was designed to study childhood wheezing and asthma, not cognition. The cognitive analysis came later, so the results should be seen as suggestive, not final proof that higher-dose vitamin D improves children’s memory.
The study also may not apply equally to everyone. Most participants were white, and many mothers already had fairly good vitamin D levels before supplementation began. The findings may look different in more diverse groups or among pregnant people with lower vitamin D levels.
It is also important to note that both groups received vitamin D. This was not a study of vitamin D versus no vitamin D. It compared a higher dose with the standard recommended dose used in Denmark at the time.
Vitamin D plays many roles in the body, and researchers are still studying how it may affect the developing brain. But the practical takeaway is not that more is always better. Vitamin D needs can vary based on diet, sun exposure, skin pigmentation, geography and baseline vitamin D levels.
For pregnant people, the safest next step is still the most familiar one: talk with a health care provider before changing supplement doses.
The study was supported by core funding for the Copenhagen Prospective Studies on Asthma in Childhood research center, including support from the Lundbeck Foundation, the Danish Ministry of Health, the Danish Council for Strategic Research and the Capital Region Research Foundation. The project also received funding from the European Research Council through the European Union’s Horizon 2020 research and innovation program.
Several authors reported grants or personal fees from foundations or companies outside the submitted work, including ALK Positive, ThermoFisher Scientific, Stallergenes Greer, the Lundbeck Foundation, the Novo Nordisk Foundation, the Tryg Foundation, Boehringer Ingelheim, Lundbeck Pharma and Otsuka Pharma Scandinavia AB.