Effects Of Probiotic Supplement On Circulating Leukocytes While Cycling In The Heat

Consuming probiotics have been proposed to improve immune responses and combatgastrointestinal disturbance that may occur while cycling in the heat. PURPOSE: To determinethe effects of a probiotic supplement on leukocyte subset responses to cycling in the heat. METHODS: Aerobically trained men (n = 27; 22 ± 3 yrs; 74.2 ± 12.4 kg; 178.3 ± 8.0 cm,3.49 ± 0.54 L·min-1) participated in this double blind, parallel, randomized controlled trial.Participants were assigned to one of three groups: 1) two weeks of probiotic supplement, 2) threedays of probiotic supplement, or 3) two weeks of placebo. On the first visit, participants provideda written informed consent, were assessed for anthropometrics and a cycling VO2max. At least72 hours later, participants provided a baseline (BL) blood sample following a 10-hour fast.After supplementation, participants returned in a similarly fasted state to complete a 90-minutecycling trial in 35 °C and a 5 km cycling time trial after a 25 min rest in a thermoneutralenvironment. Blood samples were collected before exercise (PRE), immediately post-exercise(POST), and immediately post-time trial (PTT). Samples were analyzed by an automatedhematology analyzer and assessed for total counts of leukocytes (WBC), lymphocytes (LY#),monocytes (MO#) and granulocytes (GR#). Separate two-way (group × time) repeated measuresANOVAs were used to assess changes in cells following supplementation from BL to PRE anddifferences in response to exercise from PRE to POST and PTT between groups. RESULTS: Agroup x time interaction (F = 6.295; p < 0.05) from BL to PRE was present in MO#. The three daysupplement group increased MO# from BL to PRE (p < 0.05), resulting in a difference (p = 0.030)between the placebo and three-day supplement group at PRE. No other interactions nor maineffect for group or time were present from BL to PRE. During exercise, no group x timeinteractions were observed, though main effects of time (p < 0.001) existed for all cell types.Significant increases (p < 0.001) in WBC and GR# were observed between all time points, whileMO# and LY# increased from PRE to POST and PTT, though POST and PTT were not different. CONCLUSION: Three days of probiotic supplementation may increase resting MO#, thoughprobiotic supplements have no effect on circulating leukocyte responses to exercise in the heat.