Effects of Different Vitamin D3 Formulations in Vitamin D-Deficient Adults (AMORPH-D)

The Effects of Eight Weeks of Supplementation With Two Vitamin D₃ Formulations in Adults With Subclinical and Clinical Vitamin D Deficiency: A Randomized Controlled Superiority Pilot Trial

This randomized controlled superiority pilot trial will evaluate the efficacy of two vitamin D3 formulations administered over eight weeks in adults with subclinical or clinical vitamin D deficiency. The study will compare changes in serum 25-hydroxyvitamin D concentrations between formulations, as well as the proportion of participants who will achieve vitamin D sufficiency. Both formulations are expected to improve vitamin D status, with the hypothesis that one formulation will demonstrate superior bioavailability, resulting in greater and faster increases in circulating 25-hydroxyvitamin D. The findings will provide preliminary evidence to inform formulation selection and dosing strategies for correcting vitamin D deficiency and will support the design of larger, confirmatory trials.

Study Overview

• Status: Recruiting
• Conditions: Vitamin D Deficiency
• Intervention / Treatment: Dietary supplement: Experimental 1 (powdered supplement); Dietary supplement: Experimental 2 (oily supplement)

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Sergej Ostojic, MD, PhD; Phone Number: +381112643242; Email: sergej.ostojic@chess.edu.rs

Study Locations

• Serbia
  • Belgrade, Serbia, 11000
    • Recruiting
    • Center for Health Sciences
    • Contact: Sergej M Ostojic, MD, PhD; Phone Number: +381-11-2643-242; Email: sergej.ostojic@chess.edu.rs
    • Principal Investigator: Nikola Todorovic, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults aged 18 years and over
• Serum 25(OH)D < 75 nmol/L
• BMI 18.5 - 29.9 kg/m2
• Free of clinically significant acute disorders and severe chronic diseases
• No planned travel to high-UV destinations or tanning bed use during the trial
• Willing to avoid non-study vitamin D supplements
• Able to give written informed consent and comply with study visits
• Submitted informed consent

Exclusion Criteria:

• Pregnancy of breast feeding
• Underweight or obesity
• History of any dietary supplement use within 8 weeks before screening
• Medications that materially alter vitamin D metabolism or calcium balance
• Subjects with a history of medicine or alcohol abuse
• Abnormal values for lab clinical chemistry (> 2 SD)
• Unwillingness to return for follow-up analysis
• Participation in other clinical trials within 60 days prior to screening

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Experimental 1; 2,000 IU of active ingredient (powder) per day	Dietary supplement: Experimental 1 (powdered supplement); Active powdered ingredient (2,000 IU/d)
Active Comparator: Experimental 2; 2,000 IU of active ingredient (oil) per day	Dietary supplement: Experimental 2 (oily supplement); Active oily ingredient (2,000 IU/d)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
25(OH)D	Serum levels of 25(OH)D	Change from baseline 25(OH)D at 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Total calcium	Serum levels of total calcium	Change from total calcium at 8 weeks
Ionized calcium	Serum levels of ionized calcium	Change from ionized calcium at 8 weeks
Phosphorus	Serum levels of phosphorus	Change from phosphorus at 8 weeks
Magnesium	Serum levels of magnesium	Change from magnesium at 8 weeks

Collaborators and Investigators

• Sponsor: Center for Health Sciences, Serbia
• Investigators: Study Chair: Sergej Ostojic, MD, PhD, University of California, Los Angeles

Publications and helpful links

General Publications

• Borel P, Caillaud D, Cano NJ. Vitamin D bioavailability: state of the art. Crit Rev Food Sci Nutr. 2015;55(9):1193-205. doi: 10.1080/10408398.2012.688897.
• Vieira EF, Souza S. Formulation Strategies for Improving the Stability and Bioavailability of Vitamin D-Fortified Beverages: A Review. Foods. 2022 Mar 16;11(6):847. doi: 10.3390/foods11060847.
• Dalek P, Drabik D, Wolczanska H, Forys A, Jagas M, Jedruchniewicz N, Przybylo M, Witkiewicz W, Langner M. Bioavailability by design - Vitamin D3 liposomal delivery vehicles. Nanomedicine. 2022 Jul;43:102552. doi: 10.1016/j.nano.2022.102552. Epub 2022 Mar 26.

Study record dates

Study Major Dates

• Study Start (Estimated): December 15, 2025
• Primary Completion (Estimated): May 31, 2026
• Study Completion (Estimated): June 15, 2026

Study Registration Dates

• First Submitted: December 12, 2025
• First Submitted That Met QC Criteria: December 24, 2025
• First Posted (Actual): January 5, 2026

Study Record Updates

• Last Update Posted (Actual): January 5, 2026
• Last Update Submitted That Met QC Criteria: December 24, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nutrition Disorders; Avitaminosis; Deficiency Diseases; Malnutrition; Nutritional and Metabolic Diseases; Vitamin D Deficiency
• Other Study ID Numbers: 302-27-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Data obtained through this study may be provided to qualified researchers with academic interest in vitamin D. Data will be coded, with no PHI included. Approval of the request and execution of all applicable agreements are prerequisites to the sharing of data with the requesting party.
• IPD Sharing Time Frame: Data requests can be submitted starting 9 months after article publication and the data will be made accessible for up to 24 months. Extensions will be considered on a case-by-case basis.
• IPD Sharing Access Criteria: Only qualified researchers with academic interest in vitamin D research
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No