Effect of Sugar- and Polyphenol-Rich, Diluted Cloudy Apple Juice on the Intestinal Barrier after Moderate Endurance Exercise and in Ultra-Marathon Runners.

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• Athletes have distinct nutritional needs based on their sport and level of training, in particular nutrient absorption, energy production, and time to recovery.
• Specific care with regards to intestinal barrier function should be taken given its impact on nutrient absorption and assimilation.

Introduction

The purpose of this randomised, double-blinded, partial crossover trial was to assess the effect of sugars in their natural matrix (diluted apple juice) or in water, versus water only, on the intestinal barrier (IB) during (A) moderate endurance exercise and (B) Ultra-marathon runners.

Methods

Study A: From a total enrolment of n=24, n=17 healthy, non-smoking, non-endurance, local club runners (n = 17; 14 male; 3 female) completed a 1-h endurance run at 80% of individual anaerobic threshold, which was repeated 3 times to test the response to post-exercise drinks, consumed immediately after the run and within 5 minutes of: 500 ml water, placebo (matched sugary control), or test drink (diluted 60% apple juice). Six specifically timed interval blood samples were analysed for the following intestinal barrier (IB) markers: bacterial endotoxin, interleukin 6 (IL-6), cluster of differentiation (CD14), and intestinal fatty acid-binding protein (iFABP). A 14-day washout period separated the testing of each drink.

Study B: From a total enrolment of n=30, n=10 ultra-marathoners completed the ultra-marathon. Immediately post-run they ingested the allocated beverage (water, n = 3; placebo n = 3; test drink n = 4). 4 Blood samples were taken at defined time intervals (120 and 180 minutes post-exercise) for assessment.

Results

Study A Data revealed increases in bacterial endotoxin and iFABP, (p<0.05) and a trend to increased CD14 (p = 0.05) and IL-6 (p = 0.07) with 1-hour running. The different beverages had little effect on the IB markers post-exercise: after 180 mins, placebo had less endotoxin than water and the test drink higher CD14 than placebo (both p<0.05).

Study B Data revealed increases in both bacterial endotoxin and IL-6 (p < 0.05), the latter being 20-fold more compared to the activity in study A. 180-Minutes post marathon, bacterial endotoxin values decreased irrespective of drink choice, but the differences in resulting value at 180 min were only statistically significant between placebo vs water (p < 0.05).

Conclusion

Endurance exercise, even when moderate, may increase IB markers. Of note, however, was a natural reduction in serum endotoxin and inflammatory marker IL-6 180 minutes post ultra-marathon, irrespective of which one of the three specific beverages was consumed. Furthermore, the effect of the test drink was similar to that of water.

• Endurance exercise appears to have a marked effect on intestinal permeability and bespoke nutritional support to address potential damage to the intestinal barrier should be included in an athlete’s training programme.
• Addressing chronic inflammation should similarly be considered given the negative effects on intestinal barrier function and long-term health outcomes.
• Given the outcome of this limited study it seems that post-exercise hydration options for moderate endurance exercise can include any of the three drink options.

• The results of this study were based on very small cohorts and larger populations are therefore needed to confirm these preliminary findings.
• Standardisation of diet for longer periods prior to trial is furthermore needed to ascertain participant response to various post-exercise drinks based on intestinal barrier function.
• Assessment of intestinal barrier function for an extended time period prior to trials may offer insight into individual response to specific drinks.