Fermented Whey Product Intake Is Associated With Reduced Self-perceived Gastrointestinal Symptoms In Well-trained Athletes

PURPOSE: A substantial number of athletes report gastrointestinal (GI) issues. Fermented foods with pre-and/or probiotic features may relieve GI issues by improving gut health. This study aimed to characterize GI issues and assess the effect of a fermented whey (FW) product in athletes with self-reported GI distress at inclusion. METHODS: This time-series quasi-experimental clinical trial, consisted of 1) a 3-week observation period reflected by two baseline measurements on Days 1 and 22, which was followed by 2) a 3-week intervention period (with measurements on Day 43) in which athletes with GI issues added 15 g of FW to their diet. The gastrointestinal symptom rating scale (GSRS) was the primary outcome. Secondary outcomes were physical wellbeing (assessed by PHQ), 16S fecal microbiota profiling, and self-reported diet quality (REAP). Outcomes obtained during baseline (Day 1 and Day 22 average) were compared to those after the intervention period (Day 43). Additionally, these results were compared with baseline outcomes of a reference group (RG) of athletes without GI issues. Statistical significance was set at P < 0.05. RESULTS: 50 athletes (24.7 ± 4.5 years) with GI issues and 21 RG athletes (25.4 ± 5.3 years) without GI issues were included in the study. Baseline GSRS scores were significantly different between groups: 30.3 ± 8.8 vs. 24.1 ± 8.5, respectively (F = 7.46, P = 0.008). During the observation period, 72 ± 6% of athletes with GI issues indicated having at least one severe complaint. After 3 weeks of intervention, the athletes with GI complaints reported significantly fewer severe GI complaints (54%, χ2 (4) = 24.2, P < 0.001), better physical wellbeing (F = 6.97, P = 0.010) compared to baseline, and GSRS score (27.2 ± 8.2) was not different anymore from RG (F = 2.12, P = 0.150). Preliminary results of fecal microbiota in athletes with GI complaints showed significant increases in Bifidobacterium following 3 weeks of FW supplementation compared to baseline and to RG (P < 0.01). Diet quality was good during the study for all athletes (F < 0.27, P > 0.608). CONCLUSION: After 3-week FW supplementation, self-reported severe GI discomfort scores in well-trained athletes were reduced, physical wellbeing improved, and fecal Bifidobacterium increased compared to baseline. Supported by Industry Grant of FrieslandCampina.