Divergent effects of sex and calcium/vitamin D supplementation on serum magnesium and markers of bone structure and function during initial military training.

Stephen R Hennigar,Bradley J Anderson,Erin Gaffney-Stomberg,Anna T Nakayama,James P Mcclung,Alyssa M Kelley

doi:10.1017/s0007114521004669

Abstract

Maintaining Mg status may be important for military recruits, a population that experiences high rates of stress fracture during initial military training (IMT). The objectives of this secondary analysis were to (1) compare dietary Mg intake and serum Mg in female and male recruits pre- and post-IMT, (2) determine whether serum Mg was related to parameters of bone health pre-IMT, and (3) whether Ca and vitamin D supplementation (Ca/vitamin D) during IMT modified serum Mg. Females (n 62) and males (n 51) consumed 2000 mg of Ca and 25 μg of vitamin D/d or placebo during IMT (12 weeks). Dietary Mg intakes were estimated using FFQ, serum Mg was assessed and peripheral quantitative computed tomography was performed on the tibia. Dietary Mg intakes for females and males pre-IMT were below the estimated average requirement and did not change with training. Serum Mg increased during IMT in females (0·06 ± 0·08 mmol/l) compared with males (-0·02 ± 0·10 mmol/l; P < 0·001) and in those consuming Ca/vitamin D (0·05 ± 0·09 mmol/l) compared with placebo (0·001 ± 0·11 mmol/l; P = 0·015). In females, serum Mg was associated with total bone mineral content (BMC, β = 0·367, P = 0·004) and robustness (β = 0·393, P = 0·006) at the distal 4 % site, stress-strain index of the polaris axis (β = 0·334, P = 0·009) and robustness (β = 0·420, P = 0·004) at the 14 % diaphyseal site, and BMC (β = 0·309, P = 0·009) and stress-strain index of the polaris axis (β = 0·314, P = 0·006) at the 66 % diaphyseal site pre-IMT. No significant relationships between serum Mg and bone measures were observed in males. Findings suggest that serum Mg may be modulated by Ca/vitamin D intake and may impact tibial bone health during training in female military recruits.

Highlights

Magnesium is an essential mineral that imparts critical structural and functional roles in the body
The primary objectives of this retrospective analysis of a randomized, double-blind, placebo-controlled trial were to 1) characterize dietary magnesium intake and serum magnesium concentrations in female and male recruits pre- and post-initial military training (IMT) and 2) determine whether serum magnesium was associated with parameters of bone health in female and male recruits starting military training
The major findings from the current study were 1) dietary magnesium intakes were below the Estimated Average Requirement (EAR) and hypomagnesemia was observed in a large proportion of females and males prior to and during IMT, 2) serum magnesium was associated with parameters of bone health in females, but not in males, and 3) Ca/vitamin D supplementation during IMT increased serum magnesium compared to placebo

Summary

Introduction

Magnesium is an essential mineral that imparts critical structural and functional roles in the body. A small amount of magnesium (1%) is found extracellularly and the remaining is primarily found in soft tissue, mainly skeletal muscle [1]. Magnesium in this capacity is bound to phospholipids of cell membranes or associated with enzymes where it assists with membrane stabilization or as a cofactor for enzymatic reactions, respectively. Serum magnesium concentrations within the current clinical cutoff for magnesium deficiency (i.e., subclinical or chronic latent magnesium deficiency) have been related to increased risk for many chronic diseases, including osteoporosis [5, 6]. A meta-analysis found that low serum magnesium concentrations were a risk factor for osteoporosis in postmenopausal women [1]

Methods

Results

Conclusion