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Evaluating Response to Vitamin D3 and K2 Supplementation in Healthcare Personnel
A Double-Blind Randomized Controlled Trial Evaluating Response to Vitamin D3 and K2 Supplementation Through Inflammatory Markers and the Gut Microbiome in Healthcare Personnel
Who can join
Ages 18 to 69 · All sexes · Healthy volunteers welcome
Full eligibility 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)
About the study
The main purpose of this research study is to learn about the effects of supplemental vitamin D3 and vitamin K2 on blood levels and the gut microbial community, called the gut microbiome. There are many influences on blood levels of vitamin D and K to include your dietary intake, lifestyle behaviors (physical activity, sleep), genetic alterations in metabolism of these vitamins, and the gut microbial abundance and diversity. You will be asked to take one capsule containing vitamin D3 (125 mcg), vitamin K2 (180 mcg), a combination of vitamins D3 and K2 (same doses as previous), or a placebo powder for 90 days. You will also be asked to complete questionnaires, undergo body composition and blood pressure measurements, provide blood samples and a stool swab, all on 2 occasions about 3 - 4 months apart. By conducting this study, we aim to identify the frequency of common genetic alterations in vitamins D and K metabolism and establish the impact on the gut microbiome for the first time. Your participation in this study will last about 4 - 6 months and include up to 3 visits.
What is being tested
- Vitamin Arm 1 (dietary supplement)
- Vitamin Arm 2 (dietary supplement)
- Vitamin Arm 3 (dietary supplement)
- Placebo (other)
Sponsor: Madigan Army Medical Center · Participants: 96 · Started: Mar 27, 2025
Contact the study team
- Mary S McCarthy, PhD · Phone: 253-968-3695
- Hyojin C Yi, BSN · Phone: 253-968-2898
Official record on ClinicalTrials.gov — NCT07199829
Locations in the U.S.
| Washington | Madigan Army Medical Center, Tacoma |
Conditions
From ClinicalTrials.gov, data retrieved Sep 30, 2026. Each study sets its own eligibility; the study team decides who can join.