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Large decreases in Vitamin D and Iron during military basic training – March 2017

Anabolic Adaptations Occur in Conscripts During Basic Military Training Despite High Prevalence of Vitamin D Deficiency and Decrease in Iron Status.

Mil Med. 2017 Mar;182(3):e1810-e1818. doi: 10.7205/MILMED-D-16-00113.


By week 10 decrease in serum ferritin concentration (39.3%)
% of trainees with < 20 nanograms of vitamin D

Week 1 42.6%
Week 1080.8%
Week 15 91.5%

See also VitaminDWik

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Ööpik V1, Timpmann S1, Rips L2, Olveti I3, Kõiv K4, Mooses M1, Mölder H5, Varblane A3, Lille HR3, Gapeyeva H1.

  • 1 Institute of Sport Sciences and Physiotherapy, University of Tartu, 18 Ülikooli Street, 50090 Tartu, Estonia.
  • 2 Sports Traumatology Center, Sports Medicine and Rehabilitation Clinic, Tartu University Hospital, 1a Ludvig Puusepa Street, 50406 Tartu, Estonia.
  • 3 Centre for War and Disaster Medicine, Estonian National Defence College; Estonian Defence Forces, 12 Riia Street, 51013 Tartu, Estonia.
  • 4 Estonian National Defence College, 12 Riia Street, 51013 Tartu, Estonia.
  • 5 Medical Centre of the 2nd Infantry Brigade CSS Battalion, Estonian Defence Forces, 3a Kose Road, 65603 Võru, Estonia.

In Estonian Defense Forces that are drawn up on the basis of the conscription model considerable numbers of young men are prematurely discharged from military service for medical reasons, but causes leading to premature dropout of conscripts have not been systematically studied. However, one of the factors involved could be relatively demanding physical training that starts at the beginning of military service in the form of basic military training (BMT). Cumulative training and nontraining stresses experienced by conscripts during BMT may exceed their physiological adaptability and increase the probability of becoming prematurely discharged. Therefore, the primary purpose of this study was to assess physiological responses to 10-week BMT in Estonian conscripts.

The protocol of the study confirmed to the standards set by the Declaration of Helsinki and it was approved by the Research Ethics Committee of the University of Tartu. Mean ± SD age and body mass index of 94 conscripts studied was 20.9 ± 1.7 years and 24.2 ± 3.0 kg · m-2, respectively. Fasting venous blood analysis was performed four times during BMT (October to December) and once 15 weeks after the end of BMT (in March). One-factor (time) repeated measures analysis of variance was used to evaluate the differences within the variables. Statistical significance was set at p < 0.05. Where a significant main effect was observed, Tukey's honesty significant difference post-hoc analysis was used to locate differences between the means. A Pearson product moment coefficient of correlation (r) with α level set at 0.05 was applied to determine the relationship between variables.

Significant increases in serum testosterone concentration (60.6%), testosterone to cortisol ratio (61.1%), blood erythrocyte count (4.3%), hemoglobin concentration (3.8%) and hematocrit (2.2%), and decrease in serum ferritin concentration (39.3%) occurred between weeks 1 and 10 during BMT (in all cases p < 0.0001). Fifteen weeks later, these parameters were still at increased or decreased levels, respectively, compared to week 1. The prevalence of vitamin D deficiency (serum 25(OH) D concentration <50 nmol · L-1)
increased from

  • 42.6% in week 1 to
  • 80.8% in week 10 and to
  • 91.5% 15 weeks later.

Serum 25(OH)D levels did not correlate with testosterone concentrations (r = 0.062, p = 0.552 in Wk-1 and r = -0.079, p = 0.448 in Wk-25).

These findings suggest that BMT induces anabolic physiological adaptations in conscripts despite vitamin D deficiency and decrease in iron status. However, high prevalence of vitamin D deficiency and decline in iron status may limit physiological adaptations and improvement in physical work capacity to a suboptimal level. Furthermore, as vitamin D influences a variety of functions important for health, deficiency in conscripts should be considered a major concern that needs treatment. An acknowledged limitation of the study is the lack of a control group of conscripts possessing normal vitamin D status and stable serum ferritin levels throughout the study period. Nevertheless, the research design employed enabled to determine two factors that potentially limit physiological adaptability of conscripts to military training loads in ecologically authentic environment.

PMID: 28290964 DOI: 10.7205/MILMED-D-16-00113