Vitamin D 25-Hydroxylase DeficiencyNCT07641075
Effects of High-Dose Vitamin D on Hormones, Neuromuscular Function, Cognition, and Body Composition in Athletes
A study testing Vitamin D supplementation in people with Vitamin D 25-Hydroxylase Deficiency and Vitamin D Deficiency/Insufficiency, run by The Jerzy Kukuczka Academy of Physical Education in Katowice at 1 site in Poland.
Trial summary
This study aims to evaluate the effects of high-dose vitamin D3 supplementation on selected physiological, neuromuscular, and cognitive parameters in athletes. At the baseline visit, participants will undergo a series of assessments at the Functional Research Laboratory at AWF Katowice, including a 10 mL venous blood… Read more about this study
- Who is it for?
- Ages 17 to 60 yearsHealthy volunteers can take part
- Conditions the study is for
- Vitamin D 25-Hydroxylase Deficiency, Vitamin D Deficiency/Insufficiency
- What is being tested?
- Vitamin D supplementation
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 200 participants
- Where
- 1 sitePoland
- Study dates
- 1 Jul 2025to 31 Dec 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 17 to 60 years
- All sexes
- Healthy volunteers accepted
- Child, Adult
Who may be able to join
- a minimum of 8 years of training experience,
- absence of injuries in the 6 months leading up to the assessments,
- consistent engagement in training sessions a minimum of 5 times per week over the last 6 months.
Who cannot join
- vitamin D supplementation within one month prior to the study,
- use of multivitamin supplements,
- intestinal disorders.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Poland1 site, 1 recruiting
- Recruiting
The Jerzy Kukuczka Academy of Physical Education in Katowice
Katowice, Mikołowska 72a, 40-065
Małgorzata Michalczyk, 535016532, m.michalczyk@awf.katowice.pl
About this study
Official title: The Effect of High-dose Vitamin D Supplementation on Selected Hormone Concentrations, Neuromuscular Transmission, Athletic Performance, Cognitive Functions, and Body Composition in Athletes.
This study aims to evaluate the effects of high-dose vitamin D3 supplementation on selected physiological, neuromuscular, and cognitive parameters in athletes. At the baseline visit, participants will undergo a series of assessments at the Functional Research Laboratory at AWF Katowice, including a 10 mL venous blood sample collection, body composition analysis (via InBody and DEXA scans), neuromuscular function evaluation using tensiomyography (TMG), and computerized cognitive tests via the Vienna Test System.
Following baseline testing, participants will be randomly assigned to either the vitamin D3 group or the placebo group. The active group will receive a daily dose of 4,000 IU of vitamin D3 (1 capsule with dinner), while the control group will receive an identical placebo. The intervention period will last for 4 or 8 weeks. Upon completion of the supplementation period, all baseline assessments will be repeated to evaluate the post-intervention changes.
Read the detailed description
For the first visit, the participant is invited to the Functional Research Laboratory at the Academy of Physical Education (AWF) in Katowice. The visit will be initiated with a blood sample collection (10 mL) from the cubital vein, which will be followed by body mass and body composition measurements. These measurements will be performed using the InBody device (in a standing position, in light clothing or underwear) and a DEXA scan (in a supine position, in light clothing), which is utilized to evaluate bone and fat tissue using a minimal dose of X-ray radiation.
As the next stage, a tensiomyographic (TMG) assessment will be conducted in a supine position and in underwear. Single-use electrodes will be attached to the biceps brachii (long head) of both upper limbs and the gastrocnemius (lateral head) of both lower limbs. A completely non-invasive, very low-voltage and low-intensity electrical current will be emitted by an electrostimulator in order to induce muscle contraction and measure its response speed. This assessment will be performed at rest, without a warm-up, is entirely harmless, and can be repeated.
Subsequently, cognitive function tests will be performed using the computerized Vienna Test System (SCHUHFRIED GmbH, Austria). The first test involves reading color-words and naming colors, while the second test involves reading words in an incongruent color and naming colors with an incongruent meaning. Responses will be provided by pressing one of four buttons on a specialized keyboard (time limit: 2500 ms per trial). Each diagnostic block (60 trials) will be preceded by a practice block (10 trials).
Following the completion of all assessments, the participant will be randomly assigned to one of two groups: the supplemented group (vitamin D3) or the placebo group. The randomization into groups will be carried out using balls placed in a black bag. Depending on the assigned group, and once the 25(OH)D3 level results are obtained by the research team (the next business day), the supplement in an appropriate dose or a placebo product will be allocated. The collection of the products will take place on the 3rd day from the start of the project. The dose of vitamin D3 will be of 4,000 IU/day. If assignment to the placebo group occurs during randomization, a placebo supplement will be provided. The supplements will be consumed 1 capsule in the evening (with dinner). The supplementation period will last for 4 or 8 weeks.
After 4 or 8 weeks of supplementation, the study will be concluded, at which point the participant will be invited to AWF again, where all assessments from stage 1 will be repeated.
- Being tested
- Vitamin D supplementation, Placebo
- Keywords
- vitamin D, athletes, coggnitive function, neuro-muscular function, hormones, speed, performance
- Medical subject headings
- Vitamin D Hydroxylation-Deficient Rickets, Type 1B, Vitamin D Deficiency
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Vitamin D supplementationDietary supplement
Vitamin D3 will be administered orally in the form of capsules. Participants will ingest a total daily dose of 4,000 IU, split into two doses: 1 capsule (4,000 IU) in the evening with dinner. The intervention will be carried out daily for a duration of either 4 or 8 weeks. Supplementation compliance will be monitored by the research team through capsule counting during follow-up visits.
PlaceboDietary supplement
An identical placebo will be administered orally in the form of capsule, matching the active vitamin D3 supplement in appearance, size, color, and taste. Participants will ingest 1 placebo capsule in the evening with dinner daily for a duration of either 4 or 8 weeks.
| Study group | Role | What they receive |
|---|---|---|
| Vitamin D3 supplemented group | Experimental | Participants in this arm will receive vitamin D3 supplementation at a total daily dose of 4,000 IU. The supplement will be administered 1 capsule in the evening (with dinner). The intervention period will last for either 4 or 8 weeks. Receives: Dietary Supplement: Vitamin D supplementation |
| Placebo supplementation group | Placebo comparator | Participants in this arm will receive placebo supplementation. The supplement will be administered capsule in the evening (with dinner). The intervention period will last for either 4 or 8 weeks. Receives: Dietary Supplement: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Serum 25-Hydroxyvitamin D Concentration
Description: Serum concentration of 25-hydroxyvitamin D [25(OH)D] measured using a validated laboratory method to assess vitamin D status.
Unit of Measure: ng/mL
Measured: 8-weeks
Secondary outcomes (3)
Corsi Block-Tapping Test - Block Time
Description: Visuospatial working memory assessed using the Corsi Block-Tapping Test. Block Time represents the reaction time required to complete the task.
Unit of Measure: ms
Measured: 8-weeks
Corsi Block-Tapping Test - Reverse Span Score
Description: Visuospatial working memory performance assessed using the reverse recall condition of the Corsi Block-Tapping Test.
Unit of Measure: score
Measured: 8-weeks
Corsi Block-Tapping Test - Unweighted Block Span
Description: Maximum sequence length correctly reproduced during the Corsi Block-Tapping Test.
Unit of Measure: blocks
Measured: 8-weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Jun 2026
- Study start1 Jul 2025
- Primary completion10 Jul 2025
- Study completion31 Dec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Vitamin D 25-Hydroxylase DeficiencyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 200 participants (estimated)
Sponsor and investigators
- Lead sponsor
- The Jerzy Kukuczka Academy of Physical Education in Katowice
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Małgorzata Magdalena Michalczyk, The Jerzy Kukuczka Academy of Physical Education in Katowice
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07641075
- Sponsor's protocol ID
- KB-05/2017
- Other IDs
- Institute of Sport Sciences
- Status last verified
- May 2026
- First submitted
- 20 May 2026
- Last updated
- 11 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes
Publications
Michalczyk MM, Gepfert M, Roczniok R, Zydek G. Eight-Week Vitamin D3 Supplementation at 4000 IU/Day Was Not Associated with Further Improvements in Speed or Power Performance in Professional Female Soccer Players: A Randomized Controlled Trial. Nutrients. 2026 Jul 28;18(15):2460. doi: 10.3390/nu18152460.
PubMed 42588083
Study at a glance
From the registry record, last updated by the sponsor on 11 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effect of High-dose Vitamin D Supplementation on Selected Hormone Concentrations, Neuromuscular Transmission, Athletic Performance, Cognitive Functions, and Body Composition in Athletes.
- ClinicalTrials.gov ID
- NCT07641075
- Acronym / sponsor ID
- KB-05/2017
- Keywords
- vitamin D, athletes, coggnitive function, neuro-muscular function, hormones, speed, performance
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 200 participants (estimated)
- Lead sponsor
- The Jerzy Kukuczka Academy of Physical Education in KatowiceUniversity, hospital or other
- Study start
- 1 Jul 2025 (actual)
- Primary completion
- 10 Jul 2025 (actual)
- Study completion
- 31 Dec 2028 (estimated)
- First posted
- 11 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study aims to evaluate the effects of high-dose vitamin D3 supplementation on selected physiological, neuromuscular, and cognitive parameters in athletes. At the baseline visit, participants will undergo a series of assessments at the Functional Research Laboratory at AWF Katowice, including a 10 mL venous blood sample collection, body composition analysis (via InBody and DEXA scans), neuromuscular function evaluation using tensiomyography (TMG), and computerized cognitive tests via the Vienna Test System.
Following baseline testing, participants will be randomly assigned to either the vitamin D3 group or the placebo group. The active group will receive a daily dose of 4,000 IU of vitamin D3 (1 capsule with dinner), while the control group will receive an identical placebo. The intervention period will last for 4 or 8 weeks. Upon completion of the supplementation period, all baseline assessments will be repeated to evaluate the post-intervention changes.
Detailed description
For the first visit, the participant is invited to the Functional Research Laboratory at the Academy of Physical Education (AWF) in Katowice. The visit will be initiated with a blood sample collection (10 mL) from the cubital vein, which will be followed by body mass and body composition measurements. These measurements will be performed using the InBody device (in a standing position, in light clothing or underwear) and a DEXA scan (in a supine position, in light clothing), which is utilized to evaluate bone and fat tissue using a minimal dose of X-ray radiation.
As the next stage, a tensiomyographic (TMG) assessment will be conducted in a supine position and in underwear. Single-use electrodes will be attached to the biceps brachii (long head) of both upper limbs and the gastrocnemius (lateral head) of both lower limbs. A completely non-invasive, very low-voltage and low-intensity electrical current will be emitted by an electrostimulator in order to induce muscle contraction and measure its response speed. This assessment will be performed at rest, without a warm-up, is entirely harmless, and can be repeated.
Subsequently, cognitive function tests will be performed using the computerized Vienna Test System (SCHUHFRIED GmbH, Austria). The first test involves reading color-words and naming colors, while the second test involves reading words in an incongruent color and naming colors with an incongruent meaning. Responses will be provided by pressing one of four buttons on a specialized keyboard (time limit: 2500 ms per trial). Each diagnostic block (60 trials) will be preceded by a practice block (10 trials).
Following the completion of all assessments, the participant will be randomly assigned to one of two groups: the supplemented group (vitamin D3) or the placebo group. The randomization into groups will be carried out using balls placed in a black bag. Depending on the assigned group, and once the 25(OH)D3 level results are obtained by the research team (the next business day), the supplement in an appropriate dose or a placebo product will be allocated. The collection of the products will take place on the 3rd day from the start of the project. The dose of vitamin D3 will be of 4,000 IU/day. If assignment to the placebo group occurs during randomization, a placebo supplement will be provided. The supplements will be consumed 1 capsule in the evening (with dinner). The supplementation period will last for 4 or 8 weeks.
After 4 or 8 weeks of supplementation, the study will be concluded, at which point the participant will be invited to AWF again, where all assessments from stage 1 will be repeated.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind (participant)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Vitamin D3 supplemented group | Experimental | Dietary Supplement: Vitamin D supplementationParticipants in this arm will receive vitamin D3 supplementation at a total daily dose of 4,000 IU. The supplement will be administered 1 capsule in the evening (with dinner). The intervention period will last for either 4 or 8 weeks. |
| Placebo supplementation group | Placebo comparator | Dietary Supplement: PlaceboParticipants in this arm will receive placebo supplementation. The supplement will be administered capsule in the evening (with dinner). The intervention period will last for either 4 or 8 weeks. |
Who may qualify
- Ages
- 17 to 60 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child, Adult
Key inclusion criteria (3 listed)
- a minimum of 8 years of training experience,
- absence of injuries in the 6 months leading up to the assessments,
- consistent engagement in training sessions a minimum of 5 times per week over the last 6 months.
Key exclusion criteria (3 listed)
- vitamin D supplementation within one month prior to the study,
- use of multivitamin supplements,
- intestinal disorders.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Vitamin D supplementationVitamin D3 will be administered orally in the form of capsules. Participants will ingest a total daily dose of 4,000 IU, split into two doses: 1 capsule (4,000 IU) in the evening with dinner. The intervention will be carried out daily for a duration of either 4 or 8 weeks. Supplementation compliance will be monitored by the research team through capsule counting during follow-up visits. | Dietary supplement | Vitamin D3 supplemented group |
| PlaceboAn identical placebo will be administered orally in the form of capsule, matching the active vitamin D3 supplement in appearance, size, color, and taste. Participants will ingest 1 placebo capsule in the evening with dinner daily for a duration of either 4 or 8 weeks. | Dietary supplement | Placebo supplementation group |
Primary outcome
Serum 25-Hydroxyvitamin D Concentration
Time frame: 8-weeks
Description: Serum concentration of 25-hydroxyvitamin D [25(OH)D] measured using a validated laboratory method to assess vitamin D status. Unit of Measure: ng/mL
3 secondary outcomes
Corsi Block-Tapping Test - Block Time
Time frame: 8-weeks
Corsi Block-Tapping Test - Reverse Span Score
Time frame: 8-weeks
Corsi Block-Tapping Test - Unweighted Block Span
Time frame: 8-weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 11 Jun 2026.
- Derived from this study: PubMed 42588083Michalczyk MM, Gepfert M, Roczniok R, Zydek G. Eight-Week Vitamin D3 Supplementation at 4000 IU/Day Was Not Associated with Further Improvements in Speed or Power Performance in Professional Female Soccer Players: A Randomized Controlled Trial. Nutrients. 2026 Jul 28;18(15):2460. doi: 10.3390/nu18152460.
- Individual participant dataSharing planned: Yes
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Vitamin D supplementation in people with Vitamin D 25-Hydroxylase Deficiency and Vitamin D Deficiency/Insufficiency, run by The Jerzy Kukuczka Academy of Physical Education in Katowice at 1 site in Poland.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 11 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Poland. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Małgorzata Michalczyk, Profesor (+48535016532, m.michalczyk@awf.katowice.pl), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Serum 25-Hydroxyvitamin D Concentration (time frame: 8-weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07641075, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 11 Jun 2026.