Phase 3
Completed N=22,220
Study of Vitamin D and Omega-3 Supplementation for Preventing Diabetes
Source: ClinicalTrials.gov NCT01633177 ↗Enrolled (actual)
22,220
Serious AEs
12.0%
Results posted
Apr 2026
Primary outcomePrimary: Incident Type 2 Diabetes — 121; 109; 139; 115 Participants
◆ Published Evidence
Emerging
17citations · ~17 / year
Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial.
Summary
The VITamin D and OmegA-3 TriaL (VITAL; NCT 01169259) is an ongoing randomized clinical trial in 25,875 U.S. men and women investigating whether taking daily dietary supplements of vitamin D3 (2000 IU) or omega-3 fatty acids (Omacor® fish oil, 1 gram) reduces the risk of developing cancer, heart disease, and stroke in people who do not have a prior history of these illnesses. This ancillary study is being conducted among nondiabetic participants in VITAL and will examine whether vitamin D or fish oil prevent type 2 diabetes. Findings from this ancillary study (n=22220 without diabetes at baseline) conducted within the VITAL trial will clarify whether vitamin D and omega-3 fatty acid supplementation reduces risk of type 2 diabetes and thus will inform public health and clinical guidelines for diabetes prevention.
Linked Publications
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Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial.
Outcome Measures
| Outcome | Result | p-value |
|---|---|---|
| PRIMARY Incident Type 2 Diabetes |
121; 109; 139; 115 | — |
| SECONDARY OGTT Index of Insulin Sensitivity |
-3.3; -3.5; -5.2; -3.0 | — |
| SECONDARY OGTT Index of Beta-cell Function |
-0.8; -2.3; 2.7; -1.7 | — |
| SECONDARY HbA1c Levels |
0.2; 0.5; 0.2; 0.5 | — |
Eligibility Criteria
Participants in VITAL (NCT01169259) who have no history of diabetes mellitus at baseline are eligible to participate in this ancillary study.
Data sourced from ClinicalTrials.gov (NCT01633177) and the linked publication. Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication. Informational only — not medical advice.