By Franklin Delgado
A recent clinical trial that followed nearly 500 children in Denmark showed that those whose mothers received high-dose vitamin D supplements during pregnancy showed slight improvements on tests of verbal and visible memory and cognitive flexibility at age 10. However, no differences were observed in overall intelligence scores.
This study, published in JAMA Community Startconsidered a randomized controlled trial, stands out for its design that allows reducing bias factors. Participants were randomly assigned to groups receiving doses of 400 or 2,400 international units of vitamin D daily.
Although the results showed statistically significant improvements, they were considered modest compared to other factors relevant to cognitive development.
Recommendations for pregnant women
Despite the findings, Dr. Leana Wen, an associate professor at George Washington University and an expert on well-being cnnwarned in an interview with that medium against self-prescribing high doses of vitamin D.
Notes that pregnant women should consult their obstetrician before starting any additional supplementation. The dose used in the study was considerably higher than the commonly recommended 400 units daily.
Wen explains, at the same time, that too much vitamin D can be harmful, as it accumulates in the body and causes high levels of calcium, which could cause serious side effects, such as kidney or heart damage. The importance of addressing supplementation in the context of comprehensive prenatal care is emphasized.
Measurement of cognitive effects of vitamin D in children
To evaluate the cognitive effects of vitamin D in children in future studies, it is recommended to combine measures of vitamin D status (serum 25-OH-vitamin D levels) with validated neuropsychological tests and longitudinal or intervention designs.
Measurement of vitamin D status
- Determine levels of 25-hydroxyvitamin D in blood (25(OH)D) at baseline and during follow-up, to establish categories: deficiency, insufficiency and sufficiency.
- Record confounding factors: diet, supplementation, photovoltaic exposure, gestational age at birth, weight, comorbidities, and possible deficiencies of other micronutrients (e.g., iron and vitamin B12).
Assessment of cognitive function
- Apply standardized neuropsychological batteries that explore:
- Attention and processing speed.
- Verbal and visible memory.
- Executive functions (planning, flexibility, help watch on inhibitory).
- Language development and visuospatial skills.
- Adapt tests to age (for example, WPPSI/WISC for schoolchildren, scales of psychomotor development for preschoolers).
Study design
- Longitudinal cohorts: measure vitamin D levels in early childhood and assess cognitive functions at various time points (e.g., 3, 5, and 8 years).
- Intervention trials: comparing groups receiving vitamin D supplementation vs. placebo, measuring changes in cognitive performance before and after (e.g., 6 months).
Statistical analysis
- Use mixed models with repeated measures to estimate the trend in cognitive functions over time according to vitamin D levels, adjusting for covariates (age, sex, socioeconomic status, parental education).
- Incorporate moderation analyzes (for example, whether the effect of vitamin D differs by age, sex, or risk group) and consider attempts at causality through mediation models.
Ethical and practical considerations
- Obtain informed consent from the parents and assent from the child, according to age and local regulations.
- Standardize the time of day, environmental conditions, and test administration formats to reduce bias when evaluating cognitive performance.
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