Serum 25-hydroxyvitamin D fluctuations in military personnel during 6-month summer operational deployments in Afghanistan.
Br J Nutr. 2019 Jan 3:1-9. doi: 10.1017/S000711451800346X.
Fallowfield JL1, Delves SK1, Hill NE2, Lanham-New SA3, Shaw AM1, Brown PEH1, Bentley C4, Wilson DR2, Allsopp AJ1.
1 Applied Physiology Department,Institute of Naval Medicine,Alverstoke,Hampshire PO12 2DL,UK.
2 Royal Centre for Defence Medicine,Birmingham B15 2SQ,UK.
3 Nutritional Sciences Dept,Faculty of Health and Medical Sciences,School of Biosciences and Medicine,U. of Surrey,Guildford,SurreyGU2 7XH,UK.
4 University Hospitals Birmingham NHS Foundation Trust,Queen Elizabeth Hospital,Birmingham B15 2TH,UK.
Soldier operational performance is determined by their fitness, nutritional status, quality of rest/recovery, and remaining injury/illness free. Understanding large fluctuations in nutritional status during operations is critical to safeguarding health and well-being. There are limited data world-wide describing the effect of extreme climate change on nutrient profiles. This study investigated the effect of hot-dry deployments on vitamin D status (assessed from 25-hydroxyvitamin D (25(OH)D) concentration) of young, male, military volunteers. Two data sets are presented (pilot study, n 37; main study, n 98), examining serum 25(OH)D concentrations before and during 6-month summer operational deployments to Afghanistan (March to October/November). Body mass, percentage of body fat, dietary intake and serum 25(OH)D concentrations were measured. In addition, parathyroid hormone (PTH), adjusted Ca and albumin concentrations were measured in the main study to better understand 25(OH)D fluctuations. Body mass and fat mass (FM) losses were greater for early (pre- to mid-) deployment compared with late (mid- to post-) deployment (P<0·05). Dietary intake was well-maintained despite high rates of energy expenditure.
A pronounced increase in 25(OH)D was observed between pre- (March) and mid-deployment (June) (pilot study: 51 (sd 20) v. 212 (sd 85) nmol/l, P<0·05; main study: 55 (sd 22) v. 167 (sd 71) nmol/l, P<0·05) and remained elevated post-deployment (October/November). In contrast, PTH was highest pre-deployment, decreasing thereafter (main study: 4·45 (sd 2·20) v. 3·79 (sd 1·50) pmol/l, P<0·05). The typical seasonal cycling of vitamin D appeared exaggerated in this active male population undertaking an arduous summer deployment. Further research is warranted, where such large seasonal vitamin D fluctuations may be detrimental to bone health in the longer-term.