The study and its comparison
D-Health randomized 21,315 adults to monthly vitamin D or placebo for five years. A sampled subgroup aged at least seventy underwent telephone cognitive testing: 3,887 at year two and 3,614 at year five. [1]
The estimated score difference was 0.04 points, with a confidence interval crossing zero. The odds ratio for impairment was 1.00, also with substantial uncertainty around it. [1]
What the finding establishes
These largely vitamin-D-replete participants do not answer whether correcting severe deficiency helps an affected patient. Telephone scores are not equivalent to a trial of diagnosed dementia treatment. Funding and conflicts were not established from the abstract. The tested regimen was 60,000 IU monthly, not every dosing schedule. [1]
A hypothetical distinction
Imagine a supplement changes a blood concentration but leaves cognitive scores unchanged. The cognitive test remains the relevant endpoint.
| Detail | Interpretation |
|---|---|
| Measured outcome | Keep the endpoint specific |
| Study preparation | Not every retail product |
| Remaining uncertainty | Not resolved by a mechanism |
Sources for this article
- Vitamin D supplementation and cognition-Results from analyses of the D-Health trial.
Source consulted: 2026-09-19. This is a reference resource, not a claim that we conducted the studies or tested a product.