α-Cyclodextrin supplementation improves endurance exercise performance and reduces post-exercise fatigue in human males: a randomized, double-blind, placebo-controlled, parallel-group study

Abstract

α-Cyclodextrin (αCD), a cyclic hexasaccharide composed of six glucose units, is not digested in the small intestine but is completely fermented by gut microbes. Recently, we have reported that αCD supplementation for nonathlete men improved their 10 km biking times. However, the beneficial effects of αCD on exercise are not yet fully understood. Therefore, we conducted a randomized, double-blind, placebo-controlled, parallel-group study to confirm the reproducibility and obtain additional data, employing a larger sample size and a greater αCD dose than that used in our previous study. Age, body mass index, estimated V̇O₂ max, and Bacteroides uniformis cell number in feces were used as stratifying factors. Eighty-one healthy nonathlete men aged 20 to 49 years who had exercise habits received a placebo (n=42) or αCD (1 g/day; n=39) for 9 weeks. Similar to our previous study, αCD supplementation significantly improved endurance exercise performance (10 km biking time trial) compared with the placebo (placebo=1,126.4 ± 133.6 s, αCD=1,073.2 ± 116.7 s, p=0.016). In addition, we observed a significantly reduced visual analog scale score for post-exercise fatigue (placebo=59.0 [46.3-54.3] mm, αCD=48.8 [37.0-50.3] mm, p=0.043). The heart rate increase was lower in the αCD group than in the placebo group during exercise (placebo=152.3 ± 11.1 bpm, αCD=144.2 ± 16.3 bpm, p=0.016). These results indicate that αCD supplementation improves endurance exercise performance and reduces post-exercise fatigue in nonathlete men.

Keywords: Bacteroides uniformis; cyclic hexasaccharide; endurance exercise; gut microbiota; post-exercise fatigue; α-Cyclodextrin.

Fig. 1.

Overview of the study protocol. (a) The randomized, double-blind, placebo-controlled, parallel-group study protocol. The treatments at −3 and 9 weeks, (b) are indicated with gray arrows, and treatments at 0, 4, and 8 weeks, (c) are indicated with white arrows. αCD: α-Cyclodextrin; BMI: body mass index; VAS: visual analogue scale questionnaire for fatigue.

Fig. 2.

VAS scores for fatigue immediately after 50 min of constant load biking exercise in the placebo and αCD groups before (0 weeks) and after (4 and 8 weeks) supplementation. Fatigue levels measured using the VAS range from 0, indicating “not feeling fatigued at all” to 100, indicating “feeling extreme fatigue”. Consecutive measurements of the same individuals (dots) are connected with lines. *p<0.050 (placebo vs. αCD, rank ANCOVA). ^†p<0.050, ^†††p<0.001 (0 weeks vs. 4 weeks or 8 weeks, Wilcoxon signed-rank test). αCD: α-cyclodextrin; VAS: visual analogue scale.

Fig. 3.

Average heart rates in the last 10 min during 50 min of constant load biking exercise (Av40-50HR) in the placebo and αCD groups before (0 weeks) and after (4 and 8 weeks) supplementation. Consecutive measurements of the same individuals (dots) are connected with lines. *p<0.050 (placebo vs. αCD, ANCOVA). ^†p<0.050 (0 weeks vs. 4 weeks or 8 weeks, paired t-test). αCD: α-cyclodextrin.

Fig. 4.

Completion times of the 10 km biking time trial in the placebo and αCD groups before (0 weeks) and after (4 and 8 weeks) supplementation. Consecutive measurements of the same individuals (dots) are connected with lines. *p<0.050 (placebo vs. αCD, ANCOVA). ^†p<0.050, ^††p<0.010, ^†††p<0.001 (0 weeks vs. 4 weeks or 8 weeks, paired t-test). αCD: α-Cyclodextrin.

Fig. 5.

Cell numbers of fecal Bacteroides uniformis in the placebo and αCD groups before (0 weeks) and after (4 and 8 weeks) supplementation. Consecutive measurements of the same individuals (dots) are connected with lines. ^††p<0.010, ^†††p<0.001 (0 weeks vs. 4 weeks or 8 weeks, Wilcoxon signed-rank test). αCD: α-Cyclodextrin.