Vitamin D and DHA Show Cognitive Gains in a Year-Long Trial
Key Takeaways
-
The trial enrolled 360 older adults with mild cognitive impairment; 355 completed the year-long study.
-
Participants received vitamin D3, DHA, both supplements, or placebo.
-
Each active-treatment group improved more than placebo on cognitive measures.
-
The vitamin D3-plus-DHA group showed greater gains than either supplement alone.
-
The study also found reductions in blood markers tied to pyroptosis, an inflammatory form of cell death.
Vitamin D3 and DHA are both involved in processes relevant to brain health, but this study tested whether combining them could produce a stronger effect than either one alone.
Over 12 months, the combined group had the largest gains across full-scale, verbal, and performance IQ scores, along with improvements on several individual cognitive tasks.
The Trial at a Glance
The study randomly assigned 360 older adults with mild cognitive impairment to vitamin D3, DHA, both, or placebo. Vitamin D3 was given at 800 IU daily and DHA at 1 gram daily; 355 participants completed the 12-month trial.
Cognitive testing and blood markers were assessed at the start, six months, and 12 months, allowing the researchers to track changes over time rather than relying on a single follow-up measurement.
A Clue About Mechanism
Researchers measured five blood markers associated with pyroptosis, a form of inflammatory programmed cell death. All intervention groups saw reductions compared with placebo, with the combination again producing the strongest effect.
A decline in one protein, GSDMD, statistically accounted for part of the full-scale IQ improvement in the combined group. That does not prove cause and effect, but it offers a plausible lead for how inflammation-related biology and cognition may be connected.
What It Means for Longevity
This is a meaningful supplement study: it was randomized, double-blind, placebo-controlled, included 360 participants, and lasted a full year. But it studied people already living with mild cognitive impairment—not healthy adults seeking general prevention.
The result is promising rather than definitive. It will need replication in other populations, along with evidence on whether improved test scores translate into slower cognitive decline or better day-to-day functioning.
References:
Yuan J, Yang R, Chen H, Zhao H, Chen X, Lou Z, Han X, Ma F. Effects of a Combined Vitamin D3 and Docosahexaenoic Acid Intervention on Cognitive Function and Blood Pyroptotic Biomarkers in Older Adults with Mild Cognitive Impairment: A 12-Month Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients. 2026 Aug 25;18(17):2777. doi: 10.3390/nu18172777. PMID: 42738950; PMCID: PMC13567455.