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Randomized Controlled Trial
. 2022 Nov 29;17(11):e0277453.
doi: 10.1371/journal.pone.0277453. eCollection 2022.

No effect of a dairy-based, high flavonoid pre-workout beverage on exercise-induced intestinal injury, permeability, and inflammation in recreational cyclists: A randomized controlled crossover trial

Stephanie Kung  1 , Michael N Vakula  2 , Youngwook Kim  2 , Derek L England  2 , Janet Bergeson  1 , Eadric Bressel  2 , Michael Lefevre  1 , Robert Ward  1
Affiliations
Randomized Controlled Trial

No effect of a dairy-based, high flavonoid pre-workout beverage on exercise-induced intestinal injury, permeability, and inflammation in recreational cyclists: A randomized controlled crossover trial

Stephanie Kung et al. PLoS One. .

Abstract

Background: Submaximal endurance exercise has been shown to cause elevated gastrointestinal permeability, injury, and inflammation, which may negatively impact athletic performance and recovery. Preclinical and some clinical studies suggest that flavonoids, a class of plant secondary metabolites, may regulate intestinal permeability and reduce chronic low-grade inflammation. Consequently, the purpose of this study was to determine the effects of supplemental flavonoid intake on intestinal health and cycling performance.

Materials and methods: A randomized, double-blind, placebo-controlled crossover trial was conducted with 12 cyclists (8 males and 4 females). Subjects consumed a dairy milk-based, high or low flavonoid (490 or 5 mg) pre-workout beverage daily for 15 days. At the end of each intervention, a submaximal cycling trial (45 min, 70% VO2max) was conducted in a controlled laboratory setting (23°C), followed by a 15-minute maximal effort time trial during which total work and distance were determined. Plasma samples were collected pre- and post-exercise (0h, 1h, and 4h post-exercise). The primary outcome was intestinal injury, assessed by within-subject comparison of plasma intestinal fatty acid-binding protein. Prior to study start, this trial was registered at ClinicalTrials.gov (NCT03427879).

Results: A significant time effect was observed for intestinal fatty acid binding protein and circulating cytokines (IL-6, IL-10, TNF-α). No differences were observed between the low and high flavonoid treatment for intestinal permeability or injury. The flavonoid treatment tended to increase cycling work output (p = 0.051), though no differences were observed for cadence or total distance.

Discussion: Sub-chronic supplementation with blueberry, cocoa, and green tea in a dairy-based pre-workout beverage did not alleviate exercise-induced intestinal injury during submaximal cycling, as compared to the control beverage (dairy-milk based with low flavonoid content).

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flow diagram for the study population.
Fig 2
Fig 2. Schematic overview of the crossover study design.
Fig 3
Fig 3. Cycling performance metrics during 15-min TT.
(A) Mean cycling cadence (LFB: 93 ± 11 rpm, HFB: 93 ± 9 rpm). (B) Distance completed (LFB: 7.3 ± 0.3 km, HFB: 7.4 ± 0.3 km). (C) Work output (LFB: 174.2 ± 11.3 kJ, HFB: 180.9 ± 12.3 kJ).
Fig 4
Fig 4. Core temperature during the 1h cycling trial.
Fig 5
Fig 5. No treatment effect on plasma I-FABP pre- or post-exercise.
*Significant difference from pre-exercise, p < 0.05.
See this image and copyright information in PMC

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