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Cited by 8Vitamin D Research StudiesNutrition and Health StudiesSports Performance and Training

Seven-month wintertime supplementation of 1200 IU vitamin D has no effect on hand grip strength in young, physically active males: A randomized, controlled study

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Rips, Leho, Toom, Alar, Kuik, Rein, Varblane, Ahti, Mölder, Hanno, Tammaru, Marika, Kull, Mart, Ööpik, Vahur +3 more·2022·Journal of the International Society of Sports Nutrition
DOI 10.1080/15502783.2022.2100718PMC PMC9302007
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Abstract

Background: There has been a growing interest in the role of vitamin D for the well-being and physical performance of humans under heavy training such as conscripts in military service; however, there is a lack of long-term supplementation studies performed on members of this type of young, physically active, male population. The hypothesis of the study was that vitamin D supplementation during wintertime will decrease the prevalence of critically low vitamin D blood serum levels and increase hand grip strength during the winter season among young male conscripts. Study Design: Longitudinal, triple-blinded, randomized, placebo-controlled trial. Methods: Fifty-three male conscripts from the Estonian Army were randomized into two groups: 27 to an intervention group and 26 to a placebo group. The groups were comparable in terms of their demographics. The intervention group received 1200 IU (30 µg) capsules of vitamin D3, and the control group received placebo oil capsules once per day. The length of the follow-up was 7 months, from October 2016 until April 2017. Blood serum vitamin D (25(OH)D), parathyroid hormone (PTH), calcium (Ca), ionized calcium (Ca-i), testosterone and cortisol values, and hand grip strength were measured four times during the study period. Results: The mean 25(OH)D level decreased significantly in the control group to a critically low level during the study, with the lowest mean value of 22 nmol/l found in March 2017. At that time point, 65% in the control group vs 15% in the intervention group had 25(OH)D values of less than 25 nmol/l (p < 0.001). In the intervention group, the levels of 25(OH)D did not change significantly during the study period. All other blood tests revealed no significant differences at any time point. The corresponding result was found for hand grip strength at all time points. Conclusion: Long-term vitamin D supplementation during wintertime results in fewer conscripts in the Estonian Army with critically low serum vitamin D (25(OH)D) levels during the winter season. However, this did not influence their physical performance in the form of the hand grip strength test.

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  • Existing trials have yielded mixed findings: some reported increases in total testosterone, calculated free testosterone, bioactive testosterone, or free androgen index after supplementation, whereas others showed no meaningful change in total testosterone, SHBG, or free testosterone-related outcomes.

    “Existing trials have yielded mixed findings: some reported increases in TT, calculated FT, BAT, or FAI after supplementation, whereas others showed no meaningful change in TT, SHBG, or FT-related outcomes [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33].”

    From Vitamin D Supplementation, Total Testosterone, and Androgen Bioavailability Markers in Adult Men: A Systematic Review and Meta-Analysis of Randomized Controlled Trials (2026) · cites this paper as [22]

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Cited by

Sorted by citations

Authors
Rips, L., Toom, A., Kuik, R., Varblane, A., Mölder, H., Tammaru, M., Kull, M., Ööpik, V., Kartus, J.-T., Gapeyeva, H., & Rahu, M.
Affiliations
  • Tartu University Hospital (EE)
  • Central Finland Health Care District (FI)
  • Estonian National Defense College (EE)
  • Medical Centre of the 2nd Infantry Brigade CSS Battalion, Estonian Defence Forces, Võru, Estonia
  • East Tallinn Central Hospital (EE)
  • Jinja Hospital (UG)
  • University of Tartu (EE)
Corresponding author
Rips, Leho
ORCID
Venue
Journal of the International Society of Sports Nutrition
Publisher
Informa UK Limited
Published
2022-07-19
Volume
19
Issue
1
Pages
437-454
ISSN
1550-2783 (ISSN-L)
DOI
10.1080/15502783.2022.2100718
PMC
PMC9302007
OpenAlex
W4286218888
Cited by
8
References
5
Citations by year
2026: 2 · 2025: 1 · 2024: 2 · 2023: 2 · 2022: 1
FWCI
1.02
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of the International Society of Sports Nutrition (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Funders
Estonian Defense Forces (No. 0.4-2.5/16/1321)
Topics
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Vitamin D Research Studies
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutrition and Health Studies
  • Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
Keywords
vitamin D supplementation, vitamin D3, grip strength, 25-hydroxyvitamin D, vitamin D deficiency, conscripts, winter, physical performance, parathyroid hormone, testosterone, cortisol, calcium
MeSH terms
Calcium, Calcium, Dietary, Cholecalciferol, Humans, Male, Vitamin D, Vitamin D Deficiency, Vitamins, Hand Strength, Dietary Supplements

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