Capsule Size Alters the Timing of Metabolic Alkalosis Following Sodium Bicarbonate Supplementation

India Middlebrook, Joe Peacock, Daniel J. Tinnion, Nicholas K. Leach, Nathan P. Hilton, Bryan Saunders, S. Andy Sparks, Lars R. Mc Naughton*

*Corresponding author for this work

Research output: Contribution to journalArticle (journal)peer-review

3 Citations (Scopus)
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INTRODUCTION: Sodium bicarbonate (NaHCO3) is a well-established nutritional ergogenic aid that is typically ingested as a beverage or consumed in gelatin capsules. Whilst capsules may delay NaHCO3 release and reduce gastrointestinal (GI) side-effects compared with a beverage, it is currently unclear whether capsule size may influence acid-base responses and GI symptoms following
supplementation. AIM: To determine the effects of NaHCO3 supplementation administered in different sized capsules on acid-base responses, GI symptoms and palatability. METHODS: Ten healthy males (mean ± SD: age 20 ± 2 y; height 1.80 ± 0.09 m; weight 78.0 ± 11.9 kg) underwent three testing sessions whereby 0.3 g∙kg–1 body mass NaHCO3 was consumed in either small (size 3), medium (size 0) or large (size 000) capsules. Capillary blood samples were procured pre-ingestion and every 10 min post-ingestion for 180 min. Blood samples were analysed using a Radiometer (Radiometer ABL800, Denmark) to determine blood bicarbonate concentration ([HCO3–]) and potential hydrogen (pH). Gastrointestinal (GI) symptoms were measured using a questionnaire at the
same timepoints, whereas palatability was recorded pre-consumption. RESULTS: Capsule size had a significant effect on lag time (the time [HCO3-] changed Tlag) and the timing of peak blood [HCO3–](Tmax). Bicarbonate Tlag was significantly higher in the large (28 ± 4 min) compared with the small (13 ± 2 min) sized capsules (P = 0.009). Similarly, Tmax was significantly lower in the small capsule (13 ± 2 min) compared with both the medium (22 ± 6 min; P = 0.005) and large (28 ± 4 min; P = 0.001) sized capsules. The GI symptom scores were similar for small (3 ± 3 AU,), medium (5 ± 3 AU) and large (3 ± 3 AU) sized capsules, with no significant difference between symptom scores (F = 1.3, P = 0.310). Similarly, capsule size had no effect on palatability (F = 0.8, P = 0.409),
with similar scores between different capsule sizes. CONCLUSION: Small capsule sizes led to quicker Tlag and Tmax of blood [HCO3–] compared to medium and large capsules, suggesting that individuals could supplement NaHCO3 in smaller capsules if they aim to increase buffering capacity more quickly.
Original languageEnglish
Article number634465
JournalFrontiers in Nutrition
Early online date19 Feb 2021
Publication statusPublished - 19 Feb 2021


  • acid base balance
  • buffering
  • gastrointestinal disturbance
  • palatability
  • performance


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