Background: Gastrointestinal (GI) distress symptoms are a common running-induced experience for athletes training and competing in hot environmental conditions. GI distress symptoms may compromise exercise performance as well as carbohydrate digestion and absorption. Food components may affect the presence and severity of GI distress symptoms during running in hot environmental conditions. We examined the effect of anthocyanin-rich New Zealand blackcurrant (NZBC) extract on the GI distress symptoms during running in hot environmental conditions.

Methods: Recreationally active males (n=12, age: 28±6 yr, BMI: 24.5±1.8 kg·m-2, V ̇O2max: 56±6 mL·kg-1·min-1) volunteered. The study had a placebo-controlled, double blind, randomized, cross-over design. In thermoneutral conditions (18°C and 40% relative humidity), participants completed an incremental exercise test to exhaustion to standardize running intensity (visit 1) and a familiarization (visit 2). Participants dosed with 7-days of NZBC extract (210 mg anthocyanins per day) or placebo. Euhydration was confirmed before the experimental visits of treadmill running for 1 hr at 65%V ̇O2max in an environmental chamber (TISS Services UK, Medtead, Hampshire, UK, 34.1±0.1 °C, 40.8±0.2% relative humidity). At 0, 30 and 60 min during the running and at 60 min following recovery in thermoneutral conditions, GI distress symptoms (i.e. upper, lower and other) were recorded with a modified visual analogue scale (doi: 10.1123/ijsnem.2018-0215). Water was available ad libitum.

Results: In the placebo condition, only 2 participants (17%) reported severe symptoms. One participant reported severe dizziness and nausea in the placebo and NZBC extract condition. In the placebo condition, 11 participants (92%) reported total GI symptoms (e.g. belching, heart burn), and this was reduced to 4 participants (25%) with NZBC extract. Only one participant reported belching, nausea and stitch 60 min following recovery in the placebo condition. Upper and lower GI distress symptoms were reduced (upper, placebo: 75%, NZBC: 25% of participants; lower: placebo: 25%, NZBC extract: 17% of participants). Other GI symptoms (i.e. nausea, dizziness and stitch) were also reduced (placebo: 50%, NZBC: 25% of participants).

Conclusions: Seven days intake of anthocyanin-rich NZBC extract reduced the incidence of GI distress symptoms during one-hour of treadmill running in hot environmental conditions. For most participants, the severity of GI distress symptoms pre-supplementation was considered very mild. Future research should examine the effects of NZBC extract on running with duration and intensity in conditions for which GI distress symptoms are known to be severe.

Acknowledgements: Supplementation was provided by Health Currancy Ltd (United Kingdom) and CurraNZ Ltd (New Zealand). Financial support for conference attendance was obtained from Blackcurrant New Zealand Inc (New Zealand).