Effects of exercise in hot and humid conditions and bovine colostrum on salivary immune markers

Abstract: The purpose of this study was to examine the effects of exercise in a hot and humid environment on salivary lactoferrin and lysozyme. A secondary aim was to quantify the effects of 14-day bovine colostrum (BC) supplementation on salivary lactoferrin and lysozyme at rest and following exercise in hot and humid conditions. Using a randomized, double-blind, and counterbalanced design, ten males (20 ± 2 years, VO2max 55.8 ± 3.7 mL kg−1 min−1, 11.8 ± 2.7% body fat) ran for 46 ± 7.7 min at 95% of ventilatory threshold in a 40 °C and 50% RH environment after 14-days of supplementation with either BC or placebo. Saliva was collected pre, post, 1-h, and 4-h post exercise, and was analyzed for lactoferrin and lysozyme using ELISA. There was an immediate increase in the concentration and secretion rate of lactoferrin and lysozyme (p   0.05). Saliva flow rate was not different between conditions [(PLA: pre: 0.54 ± 0.3, post: 0.44 ± 0.3, 1-h: 0.67 ± 0.3, 4-h: 1.0 ± 0.4 mL min−1); (BC: pre: 0.58 ± 0.2, post: 0.37 ± 0.1, 1-h: 0.63 ± 0.2, 4-h: 0.83 ± 0.4 mL min−1)]. There were no differences in thermoregulatory markers (core temperature or physiological strain index) between BC and placebo trials. Interestingly, exercise-induced heat stress did not impair mucosal immune parameters, instead participants showed a transient increase in salivary lactoferrin and lysozyme. Further, 14-day BC supplementation had no effect on mucosal immunity at any time point.