(P32-009-23) Varying Macronutrient Intake Does Not Impact Biomarkers of Gastrointestinal Barrier Function During Arctic Military Training

Objectives: Intestinal barrier damage resulting from physiological stress and inflammation experienced during military training may increase intestinal permeability (IP) and worsen inflammation. Macronutrients can differentially affect intestinal barrier function, but whether manipulating macronutrient intake impacts IP during military training is unclear. This study aimed to determine the effects of varying macronutrient intakes on biomarkers of IP and their association with markers of inflammation during a strenuous military training exercise.

Methods: Soldiers (57M/11F, 19 ± 1 y) participating in eight days of arctic training were randomized to receive three rations and four supplemental snack bars (~375 kcals/bar) daily that were high-fat and energy-dense (EN-DENSE, n=22; 6.7 kcal/g, %energy carbohydrate/fat/protein: 18/77/5), whey protein and essential amino acid enriched (EAA, n=27; 4.2 kcal/g, 31/40/31) or high-carbohydrate and low-energy-dense (CON, n=19; 3.4 kcal/g, 78/11/12). Soldiers were instructed to eat all supplemental bars and consume rations (3/d) ad libitum. Energy intake (trash collection) and expenditure (D₂¹⁸O) were measured daily. Serum markers of IP (lipopolysaccharide binding protein (LBP) and zonulin) and inflammation (interleukin (IL)-6, high-sensitivity C-reactive protein (CRP), and tumor necrosis (TNF)-α) were measured before (PRE) and after (POST) training.

Results: Fat (mean ± SD: 2.7 ± 0.6 g/kg/d), protein (2.5 ± 1.5 g/kg/d), and carbohydrate (7.9 ± 1.0 g/kg/d) intakes were higher in EN-DENSE, EAA and CON, respectively, compared to the other groups (all P < 0.05). Energy intake (4045 ± 738 kcal/d) and expenditure (5341 ± 674 kcal/d) did not differ between groups (P < 0.05). LBP (median change [IQR]: 31% [76]), zonulin (8% [55]), IL-6 (11% [56]), and CRP (100% [357]) increased PRE to POST (all P < 0.05) independent of group; TNFα did not change. Increases in LBP and CRP were correlated (r = 0.43, P < 0.001), but no additional correlations between changes in outcomes were observed.

Conclusions: Findings suggest increases in biomarkers of IP during strenuous military training are not consistently associated with markers
of inflammation and are not affected by macronutrient supplementation within the intake range studied.

Funding Sources: Supported by DHP JPC-5.