Vitamin D3 and K2 for healthcare personnel
Official title: A Double-Blind Randomized Controlled Trial Evaluating Response to Vitamin D3 and K2 Supplementation Through Inflammatory Markers and the Gut Microbiome in Healthcare Personnel
Run by Madigan Army Medical Center · NCT07199829 · Data updated 2026-11-12
This study tests whether daily vitamin D3 and/or K2 supplements or a placebo change blood vitamin levels and the gut microbiome in military healthcare personnel with low vitamin D.
Quick facts
| Study type | Interventional |
|---|---|
| Ages | 18 Years to 69 Years |
| Sex | All |
| Enrollment | 96 (estimated) |
| Sponsor | Madigan Army Medical Center Federal |
| Locations | 1 site (Tacoma, Washington) |
| Status | Recruiting |
| Started | March 27, 2025 |
| Main results expected | March 2026 |
| Study ends | March 2026 |
| Registry record updated | September 30, 2025 |
| Trial ID | NCT07199829 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Ideal candidates are military beneficiaries (active duty, retired, or dependents) with 25-OHD ≤30 ng/mL who can stop vitamin D/K supplements and attend two on-site visits about 3–4 months apart.
✕Probably not a fit
Patients with malabsorption disorders, current or recent antibiotic or anticoagulant use, current weight-loss or fat-malabsorption medications, pregnancy or breastfeeding, or allergies to study ingredients are unlikely to benefit or are ineligible.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This interventional study enrolls military healthcare personnel with low 25-OHD (≤30 ng/mL) who agree to stop outside vitamin D and K supplements. Participants will take one daily capsule of vitamin D3 (125 mcg), vitamin K2 (180 mcg), a combination of both, or a placebo for 90 days and will complete questionnaires, body composition and blood pressure measurements, blood draws, and a stool swab at two visits about 3–4 months apart. The study will genotype common variants in vitamin D and K metabolism and sequence gut microbiome samples to link host genetics, blood vitamin responses, and microbial community changes. The goal is to define how supplementation and genetic differences affect vitamin status and the gut microbiome.
Why it matters
Potential benefit: If successful, the trial could identify supplement strategies that restore vitamin D and K levels and reveal microbiome changes that help tailor supplementation to individuals.
How similar studies have gone: Prior trials reliably show that vitamin D and K supplements raise blood vitamin levels, but effects on the gut microbiome and interactions with specific genetic variants remain largely untested.
Who can join: the full rules
Show full inclusion / exclusion criteria
Inclusion Criteria: * able to read and understand English * 25 OHD serum level equal to or less than 30 ng/mL * willing to discontinue vitamin D3 and/or K2 supplements for 4.5 months * military beneficiary (Active Duty, Retired, Dependent) * remaining employed at workplace for 6 months Exclusion Criteria: * Diagnosed medical condition that prevents nutrient absorption from food (e.g. Inflammatory Bowel Disease, Celiac Disease, post-Roux-en-Y/Gastric sleeve surgery) * Pregnant or breastfeeding * Current antibiotic use or within past 3 months * Current anticoagulant use or within past 3 months * Current weight loss or fat malabsorption medication use (e.g. Glucagon-Like Peptide 1 agonists, Orlistat) * Allergies or sensitivities to methylcellulose, vitamin D (D3, D2), or vitamin K (K2, Menaquinone-4, Menaquinone-7)
Where it's running
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Madigan Army Medical Center
Tacoma, Washington, United States Recruiting
Study contacts
- Principal investigator: Mary S McCarthy, PhD — Madigan AMC
- Study coordinator: Mary S McCarthy, PhD
- Email: mary.s.mccarthy1.civ@health.mil
- Phone: 253-968-3695
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.