Vitamin D Intake Tied to Better Cognition in Small Study

Researchers at Emory University's Nell Hodgson Woodruff School of Nursing have reported that older adults who said they took at least 5,000 IU of vitamin D supplements a day scored more than 13% higher on a standard cognition test than those who did not, in a study of 54 people published in the journal Sleep Medicine and announced on 19 August 2026. Every participant had both disturbed sleep and diagnosed or suspected mild cognitive impairment. Cognition was measured with the Montreal Cognitive Assessment, a short screening test scored out of 30. The difference held after the researchers adjusted for other factors, they reported, while intakes below that level showed no association with total scores. This was an observational, cross-sectional analysis of self-reported supplement use, not a trial, so it cannot show that vitamin D caused the difference in scores.

What the study measured, and what it did not

The sample was small at 54 people, all of them already at raised risk of decline, and supplement intake was reported by participants rather than verified or assigned. The researchers found no difference between vitamin D2 and D3. The work was funded by the National Institute on Aging, part of the US National Institutes of Health. Senior author Victoria Pak said that "in older adults experiencing both sleep disturbance and mild cognitive impairment, this may represent a critical window for intervention". Larger randomised trials would be needed before any causal conclusion could be drawn, and the paper does not report on whether higher intakes changed anything over time.

What this means for your supplement routine

Nothing in this study changes UK guidance or what a vitamin D label is permitted to say. For context on scale, UKHSA advises the public to consider a daily 10 microgram supplement in autumn and winter, which is 400 IU, so the intakes associated with higher scores here were more than ten times that public health figure and were not tested for safety in this analysis. The finding is a signal for researchers rather than a result anyone should act on, and it says nothing about people without sleep problems or cognitive symptoms. Readers comparing what they already buy can browse the full 1,393-product catalogue.

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This article reports published news and research and is for information only. Food supplements are not a substitute for a varied diet or medical care, and no product mentioned is intended to diagnose, treat, cure or prevent any disease. Speak to your GP or pharmacist before changing what you take, especially if you are pregnant, breastfeeding, or taking prescribed medicines.

Sources

• High-dose vitamin D may improve cognition among those at risk of dementia, study finds
• Vitamin D supplement intake is associated with better cognition in persons with sleep disturbance and mild cognitive impairment (Sleep Medicine, 2026; 146: 108960)
• High-Dose Vitamin D Linked to Better Cognitive Function

Originally reported by Medical Xpress. This article has been reviewed by Dr Tosin.