Effects of Fiber Supplementation for Four Weeks on Athletic Performance in Japanese College Athletes: A Case Study—Measurement of the Athletic Performance, Salivary Biomarkers of Stress, and Mood, Affect Balance

Abstract

Aim: In this study, we explored the effects of dietary fiber on athletic performance. Methods: Twenty healthy college athletes (male/female, 1/1) consumed 6 grams of dietary fiber (Fiberpro, Taiyo Lab Inc., Tokyo) daily for four weeks and were evaluated for their athletic performance, salivary biomarkers of stress (α-amylase activity pre-post exercise, cortisol, melatonin, and secretory immunoglobulin A (SIgA) levels), and mood/affect using the Profile of Mood State 2 nd edition (POMS 2 ® ). Measurements were taken at baseline (before supplementation), at Week 4 (after 4 weeks of supplementation), and at Week 8 (4 weeks after the completion of supplementation). Results: Results showed that athletic performance and exercise-induced elevation in salivary α-amylase activity improved with Fiberpro supplementation in both men and women. Further, the Anger-Hostility scale in POMS was significantly elevated in men; in women, an increase in Vigor-Activity score, a single index of positive mood, was noted. These findings suggest that Fiberpro may induce differential affective responses in men and women. Meanwhile, Fiberpro did not affect the normal diurnal changes in salivary melatonin and SIgA levels, but it appeared to augment the normal circadian patterns of cortisol, an effect that persisted for a month without Fiberpro intake. We propose that boosting fiber intake in young, healthy athletes may improve gut microbiota and confer resilience against stress.