Vitamin D and IQ: Does Low Vitamin D Lower Intelligence? | Riot IQ
Oct 11, 2026·Advanced Topics & Research
Vitamin D and IQ: Does Low Vitamin D Lower Intelligence?
Vitamin D and IQ are only weakly linked: in 7,065 UK children, low maternal vitamin D in pregnancy did not predict IQ at 8, and trials show no cognitive gain.
Dr. Russell T. WarneChief Scientist
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Vitamin D and IQ are only weakly linked: in the largest pregnancy study, covering 7,065 mother-child pairs in England, a mother's vitamin D deficiency was not associated with her child's IQ at age 8, and randomized trials have found that vitamin D supplements do not improve cognition in people who are not deficient. Some smaller cohorts report gaps of 2 to 4 IQ points, but they disagree on who is affected and when.
This page covers the pregnancy and childhood studies, the adult research on vitamin D and cognitive decline, what the supplementation trials and genetic studies show, and why low vitamin D keeps turning up alongside poor health and lower scores.
Vitamin D in pregnancy and a child's IQ
Vitamin D status is measured as the blood level of 25-hydroxyvitamin D, written 25(OH)D. Most of the research on IQ asks whether children whose mothers had low levels during pregnancy score lower later on.
The biggest study comes from the Avon Longitudinal Study of Parents and Children (ALSPAC) in England. Andrea Darling and colleagues linked maternal 25(OH)D in pregnancy to the development of 7,065 children. Children of deficient mothers (below 50 nanomoles per liter) were slightly more likely to score in the lowest quarter for gross-motor and fine-motor development at 30 months, with odds ratios of about 1.2. At older ages the picture changed: the authors found no association with any outcome they measured, including IQ at age 8 and reading at age 9.
An earlier and much smaller Southampton study by Catharine Gale and colleagues found no association between maternal vitamin D in late pregnancy and children's intelligence at age 9, though only 178 children were tested at that age.
Other cohorts report modest links. In the Odense Child Cohort in Denmark, Eva Cantio and colleagues gave the Wechsler Intelligence Scale for Children to 1,404 seven-year-olds. Low vitamin D in early pregnancy was associated with a full-scale IQ about 2.5 points lower (95% confidence interval -4.6 to -0.3), an association driven mainly by boys. Low cord-blood levels predicted lower IQ only in boys, and a child's own low level at age 7 predicted lower IQ only in girls. A pattern that changes by sex and timing in this way is hard to interpret and may partly reflect chance across many comparisons.
In the United States, Melissa Melough and colleagues studied 1,019 mother-child pairs in the CANDLE cohort in Tennessee, where 45.6% of the mothers were vitamin D deficient in the second trimester. Each 10 nanograms per milliliter of higher maternal 25(OH)D was linked to a full-scale IQ about 1.17 points higher on the Stanford-Binet at ages 4 to 6 (95% CI 0.27 to 2.06). A later study by the same lead author in 912 children from the Environmental influences on Child Health Outcomes (ECHO) program found a similar-sized link with overall and fluid cognition scores at ages 7 to 12, and none with crystallized knowledge.
Taken together, these studies point to a small association at most, of a few points in some samples and none in the largest one. All of them are observational, so they cannot show that vitamin D itself is responsible.
Vitamin D and cognitive decline in adults
In older adults the observational link is clearer. A 2012 meta-analysis by Thorleif Etgen and colleagues pooled seven studies with 7,688 participants and found that people with low vitamin D had more than twice the odds of cognitive impairment (odds ratio 2.39). The authors listed reverse causality among the main limitations of these studies.
A broader 2017 meta-analysis by Amy Goodwill and Cassandra Szoeke, covering 26 observational studies, found a weaker association, with odds ratios of about 1.24 for worse cognitive performance and 1.26 for cognitive decline. Cross-sectional studies showed stronger effects than longitudinal ones, the pattern one would expect if part of the association comes from ill health lowering vitamin D. Whether higher general ability protects against later decline is a separate question, covered in our page on IQ and dementia.
What happens when people take vitamin D?
Randomized trials remove most of the confounding, and they have been consistently disappointing for cognition.
• Infants: In a Finnish trial, Soile Tuovinen and colleagues randomly assigned healthy infants to a standard or a three-times-higher daily vitamin D dose from 2 weeks to 2 years of age. The 801 children followed up showed no differences in developmental milestone scores at 12 or 24 months, and the higher dose was associated with a greater risk of high externalizing-problem scores.
• Young adults: In an Australian trial, Angela Dean and colleagues gave 128 healthy young adults a high-dose vitamin D capsule or a placebo daily for six weeks. Vitamin D levels rose in the treated group, yet none of the primary measures of executive function, such as working memory, changed.
• Older adults: In two substudies of the VITAL trial, Jae Hee Kang and colleagues followed more than 4,000 adults aged 60 and over who took vitamin D3 or a placebo for two to three years. The rate of cognitive decline did not differ between groups, and there was no interaction with participants' starting vitamin D levels. A possible benefit among Black participants needs confirmation.
Goodwill and Szoeke's pooled estimate from intervention studies was a standardized difference of 0.21, which would be about 3 points on an IQ-style scale, but it was not statistically significant (95% CI -0.05 to 0.46) and rested on only three trials.
Genetics points the same way. Mendelian randomization uses gene variants that nudge vitamin D levels up or down as a natural experiment, since those variants are assigned at conception and are not affected by later illness. Analyzing 172,349 participants from 17 cohorts, Janine Maddock and colleagues found that variants lowering vitamin D were not associated with poorer cognitive function. They concluded there was no evidence that 25(OH)D is a causal factor for cognitive performance in mid to later life.
Why low vitamin D tracks poor health and lower scores
The skin makes vitamin D in sunlight, so blood levels partly reflect how much time people spend outdoors, which in turn depends on health and circumstances. Skin pigmentation matters too: the ECHO authors note that low levels are especially common among people with darker skin, and in their study the association looked stronger among children of Black mothers, although the difference by race was not statistically significant.
Philippe Autier and colleagues reviewed 290 prospective cohort studies and 172 randomized trials across many health outcomes. Low 25(OH)D was consistently associated with disease in the cohort studies, including declining cognitive function, while supplementation trials did not show the matching benefits. Their interpretation was that low vitamin D is largely a marker of ill health, because inflammation and illness lower 25(OH)D. They also pointed to lifestyle changes brought on by ill health. The same reasoning applies to cognition, since people who are unwell or less mobile tend to spend less time outdoors.
Vitamin D belongs with the wider evidence on whether diet or nutrition affect IQ, where the clearest effects come from serious deficiencies in early life, such as iodine deficiency in pregnancy. None of the trials suggests that vitamin D is a route to a higher score, and our overview of whether you can increase your IQ explains why lasting gains are hard to find. Anyone concerned about their vitamin D status should ask a primary care clinician, who can order a blood test; during pregnancy, the obstetric clinician or midwife is the right person to ask.
Frequently asked questions
Does vitamin D deficiency lower IQ?
The evidence suggests a small effect at most. The largest pregnancy study found no link with child IQ at age 8, while some smaller cohorts report differences of about 2 to 4 points that vary by sex and timing.
Can vitamin D supplements raise IQ?
No trial has shown that they do. Trials from infancy to old age found no cognitive benefit from vitamin D compared with a placebo or a standard dose.
Does vitamin D in pregnancy affect a baby's intelligence?
Some cohorts link higher maternal vitamin D to slightly better child cognitive scores, but the largest study found no association with IQ. Pregnant women with questions about vitamin D should talk to their obstetric clinician or midwife.
Why is low vitamin D linked to memory problems in older adults?
Much of the link probably runs the other way: illness, frailty and less time outdoors lower vitamin D. Genetic studies and a large trial found no evidence that raising vitamin D protects cognition.
Should I get my vitamin D level tested?
A primary care clinician can decide whether a blood test makes sense based on your health and risk factors. Testing is about physical health, and it is not a way to assess intelligence.
The takeaway
Low vitamin D shows up alongside lower cognitive scores in some studies, but the association is small and inconsistent, and much of it reflects health and lifestyle. The largest pregnancy cohort found no link with child IQ. Genetic studies find no causal effect on cognition, and randomized trials of supplements have not improved thinking at any age studied. If you want an accurate picture of your reasoning abilities, a supplement will not change it, but you can take a full-length online IQ test.
References
1. Darling, A. L., Rayman, M. P., Steer, C. D., Golding, J., Lanham-New, S. A., & Bath, S. C. (2017). Association between maternal vitamin D status in pregnancy and neurodevelopmental outcomes in childhood: Results from the Avon Longitudinal Study of Parents and Children (ALSPAC). British Journal of Nutrition, 117(12), 1682-1692. [doi.org/10.1017/S0007114517001398](. doi.org
2. Gale, C. R., Robinson, S. M., Harvey, N. C., Javaid, M. K., Jiang, B., Martyn, C. N., Godfrey, K. M., Cooper, C., & the Princess Anne Hospital Study Group. (2008). Maternal vitamin D status during pregnancy and child outcomes. European Journal of Clinical Nutrition, 62(1), 68-77. [doi.org/10.1038/sj.ejcn.1602680](. doi.org
3. Cantio, E., Bilenberg, N., Nørgaard, S. M., Beck, I. H., Möller, S., Cantio, C., Jensen, T. K., Mortensen, N. B., Rasmussen, A., & Christesen, H. B. T. (2023). Vitamin D status in pregnancy and childhood associates with intelligence quotient at age 7 years: An Odense child cohort study. Australian and New Zealand Journal of Psychiatry, 57(7), 1062-1072. [doi.org/10.1177/00048674221116027](. doi.org
4. Melough, M. M., Murphy, L. E., Graff, J. C., Derefinko, K. J., LeWinn, K. Z., Bush, N. R., Enquobahrie, D. A., Loftus, C. T., Kocak, M., Sathyanarayana, S., & Tylavsky, F. A. (2021). Maternal plasma 25-hydroxyvitamin D during gestation is positively associated with neurocognitive development in offspring at age 4-6 years. Journal of Nutrition, 151(1), 132-139. [doi.org/10.1093/jn/nxaa309](. doi.org
5. Melough, M. M., McGrath, M., Palmore, M., Collett, B. R., Kerver, J. M., Hockett, C. W., Schmidt, R. J., Kelly, R. S., Lyall, K., Zhao, Q., Hipwell, A. E., Korrick, S. A., Gilbert-Diamond, D., Weiss, S. T., Chu, S. H., Mirzakhani, H., Porter, J. M., Sathyanarayana, S., & ECHO Cohort Consortium. (2025). Gestational vitamin D concentration and child cognitive development: A longitudinal cohort study in the Environmental influences on Child Health Outcomes Program. American Journal of Clinical Nutrition, 122(2), 571-581. [doi.org/10.1016/j.ajcnut.2025.06.017](. doi.org
6. Etgen, T., Sander, D., Bickel, H., Sander, K., & Förstl, H. (2012). Vitamin D deficiency, cognitive impairment and dementia: A systematic review and meta-analysis. Dementia and Geriatric Cognitive Disorders, 33(5), 297-305. [doi.org/10.1159/000339702](. doi.org
7. Goodwill, A. M., & Szoeke, C. (2017). A systematic review and meta-analysis of the effect of low vitamin D on cognition. Journal of the American Geriatrics Society, 65(10), 2161-2168. [doi.org/10.1111/jgs.15012](. doi.org
8. Tuovinen, S., Räikkönen, K., Holmlund-Suila, E., Hauta-Alus, H., Helve, O., Rosendahl, J., Enlund-Cerullo, M., Kajantie, E., Valkama, S., Viljakainen, H., Mäkitie, O., Andersson, S., & Heinonen, K. (2021). Effect of high-dose vs standard-dose vitamin D supplementation on neurodevelopment of healthy term infants: A randomized clinical trial. JAMA Network Open, 4(9), e2124493. [doi.org/10.1001/jamanetworkopen.2021.24493](. doi.org
9. Dean, A. J., Bellgrove, M. A., Hall, T., Phan, W. M., Eyles, D. W., Kvaskoff, D., & McGrath, J. J. (2011). Effects of vitamin D supplementation on cognitive and emotional functioning in young adults: A randomised controlled trial. PLoS ONE, 6(11), e25966. [doi.org/10.1371/journal.pone.0025966](. doi.org
10. Kang, J. H., Vyas, C. M., Okereke, O. I., Ogata, S., Albert, M., Lee, I.-M., D'Agostino, D., Buring, J. E., Cook, N. R., Grodstein, F., & Manson, J. E. (2021). Effect of vitamin D on cognitive decline: Results from two ancillary studies of the VITAL randomized trial. Scientific Reports, 11, 23253. [doi.org/10.1038/s41598-021-02485-8](. doi.org
11. Maddock, J., Zhou, A., Cavadino, A., Kuźma, E., Bao, Y., Smart, M. C., Saum, K.-U., Schöttker, B., Engmann, J., Kjærgaard, M., Karhunen, V., Zhan, Y., Lehtimäki, T., Rovio, S. P., Byberg, L., Lahti, J., Marques-Vidal, P., Sen, A., Perna, L., ... Hyppönen, E. (2017). Vitamin D and cognitive function: A Mendelian randomisation study. Scientific Reports, 7, 13230. [doi.org/10.1038/s41598-017-13189-3](. doi.org
12. Autier, P., Boniol, M., Pizot, C., & Mullie, P. (2014). Vitamin D status and ill health: A systematic review. The Lancet Diabetes & Endocrinology, 2(1), 76-89. [doi.org/10.1016/S2213-8587(13)70165-7](. doi.org
Hero image: Softgels, by Globallystoners, CC0. Via Wikimedia Commons.
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