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Evaluating Response to Vitamin D3 and K2 Supplementation in Healthcare Personnel

Madigan Army Medical Center · NCT07199829

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Opens the official ClinicalTrials.gov record, with the study team’s contacts. Bored Studies doesn’t enroll anyone.

Key facts

Compensation
Not posted. Ask the study team before screening.
Who can join
Ages 18–69 · All sexes
Healthy volunteers
Accepted
Study type
Interventional · Not applicable
Target enrollment
96
US sites recruiting
1
Study start
March 27, 2025
Record last updated
September 30, 2025

Status re-checked against ClinicalTrials.gov within the last 12 hours.

What the study is about

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.

Being studied: Vitamin Arm 1; Vitamin Arm 2; Vitamin Arm 3; Placebo

Conditions: Hypovitaminosis D; Hypovitaminosis

Eligibility criteria

Copied from the official record. The study team makes the final decision at screening.

Show full 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)

Recruiting US locations

  • Madigan Army Medical Center

    Tacoma, WA 98431

    Site contact: Mary S McCarthy, PhD · 253-968-3695 · mary.s.mccarthy1.civ@health.mil

Study contacts (from the official record)

  • Mary S McCarthy, PhD · 253-968-3695 · mary.s.mccarthy1.civ@health.mil
  • Hyojin C Yi, BSN · 253-968-2898 · hyojin.c.yi.ctr@health.mil
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Evaluating Response to Vitamin D3 and K2 Supplementation in… (NCT07199829) | Bored Studies