The Effects of Gastro-Resistant Sodium Bicarbonate Supplementation on Markers of Acid-Base Balance, Gastrointestinal Symptoms and Exercise Performance


Student thesis: Doctoral Thesis


Sodium bicarbonate (NaHCO3) is an extracellular buffering agent and nutritional ergogenic aid that can improve high-intensity exercise performance. Based upon prior research, NaHCO3 supplementation can improve markers of exercise metabolism, recovery and performance due to its ability to augment extracellular buffering capacity and delay exercise-induced fatigue. Nevertheless, gastrointestinal (GI) side-effects are widely reported following NaHCO3 ingestion, which might deter athletes from using NaHCO3 or confound the benefits of supplementation. When combined with gastric acid, NaHCO3 produces excess carbon dioxide that can lead to various GI symptoms, including stomach cramps, bowel urgency and diarrhoea. Bypassing the stomach presents a novel strategy to prevent GI symptoms, which may be achieved using gastro-resistant capsules. Gastro-resistant NaHCO3 could therefore offer a convenient and practical strategy to reduce GI symptoms associated with NaHCO3 supplementation, whilst improving exercise performance. Nevertheless, the efficacy of enteric-coated NaHCO3 supplementation has yet to be investigated. The subsequent investigations were conducted to further explore the effect of gastro-resistant NaHCO3 supplementation on GI symptoms, acid-base responses and high-intensity exercise performance in recreationally trained and trained males. Given that delayed-release capsules are suggested to bypass the stomach and reduce GI symptoms caused by acidic-sensitive compounds (such as NaHCO3), this was investigated in Study 1. Compared with the solution, delayed-release NaHCO3 reduced the prevalence and severity of GI symptoms and slowed metabolic alkalosis, although the overall acid-base responses (e.g. peak blood [HCO3–] and pH) were similar. Nevertheless, it was unclear whether these affects were related to encapsulation or the gastro-resistant properties of the capsule. Based on these findings, it could also be suggested that enteric-coated NaHCO3, which are more gastro-resistant than delayed-release capsules, could further reduce GI symptoms. Study 2 therefore investigated the effects of different gastro-resistant capsules (i.e. delayed-release and enteric-coated) compared with a standard capsule (i.e. gelatine) on GI symptoms and acid-base responses. Gastro-resistant capsules mitigated GI symptoms compared with the gelatine capsule, suggesting that bypassing the stomach is an efficacious strategy to reduce GI symptoms following NaHCO3 ingestion. Whilst enteric-coated NaHCO3 resulted in the fewest (and less severe) GI symptoms, acid-base responses were blunted with this ingestion form. Study 3 therefore investigated whether enteric-coated NaHCO3 could still improve high-intensity exercise performance. Enteric-coated NaHCO3 improved exercise performance during a 4 km cycling time trial in trained males, although the magnitude of effect was lower than with gelatine capsules. Collectively, these studies demonstrate that bypassing the stomach is an efficacious strategy to reduce GI symptoms with NaHCO3 supplementation, which can be achieved using gastro-resistant capsules. gastro-resistant NaHCO3 can therefore be used to mitigate GI symptoms, although these findings also suggest they should not replace standard ingestion forms in those who can tolerate them. Based on the available evidence, practical recommendations are provided for athletes which will develop as further research is conducted in this area. With this knowledge, further explorations into different gastro-resistant ingestion forms can be made, which in turn, can refine this novel and practical ingestion strategy.
Date of Award19 May 2020
Original languageEnglish
Awarding Institution
  • Edge Hill University
SupervisorLARS MCNAUGHTON (Director of Studies) & Andy Sparks (Supervisor)

Research Groups

  • Sports Performance, Exercise and Nutrition Research Group

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