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

Abstract

Introduction: Sodium bicarbonate (NaHCO₃) is a well-established nutritional ergogenic aid that is typically ingested as a beverage or consumed in gelatine capsules. While capsules may delay the release of NaHCO₃ and reduce gastrointestinal (GI) side effects compared with a beverage, it is currently unclear whether the capsule size may influence acid-base responses and GI symptoms following supplementation. Aim: This study aims to determine the effects of NaHCO₃ supplementation, administered in capsules of different sizes, on acid-base responses, GI symptoms, and palatability. Methods: Ten healthy male subjects (mean ± SD: age 20 ± 2 years; height 1.80 ± 0.09 m; weight 78.0 ± 11.9 kg) underwent three testing sessions whereby 0.3 g NaHCO₃/kg of body mass 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 analyzed using a radiometer (Radiometer ABL800, Denmark) to determine blood bicarbonate concentration ([ ${\text{HCO}}_3^{-}$ ]) and potential hydrogen (pH). 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 [ ${\text{HCO}}_3^{-}$ ] changed, T _lag) and the timing of peak blood [ ${\text{HCO}}_3^{-}$ ] (T _max). Bicarbonate T _lag was significantly higher in the large-sized (28 ± 4 min) compared with the small-sized (13 ± 2 min) capsules (P = 0.009). Similarly, T _max was significantly lower in the small capsule (94 ± 24 min) compared with both the medium-sized (141 ± 27 min; P < 0.001) and the large-sized (121 ± 29 min; P < 0.001) capsules. The GI symptom scores were similar for small-sized (3 ± 3 AU), medium-sized (5 ± 3 AU), and large-sized (3 ± 3 AU) 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 T _lag and T _max of blood [ ${\text{HCO}}_3^{-}$ ] concentration compared to medium and large capsules, suggesting that individuals could supplement NaHCO₃ in smaller capsules if they aim to increase extracellular buffering capacity more quickly.

Keywords: acid base balance; buffering; gastrointestinal disturbance; palatability; performance.

Figure 1

Mean (±SD) temporal blood pH (A) and bicarbonate concentration [${\text{HCO}}_3^{-}$] (B) responses following the consumption of 0.3 g·kg⁻¹ body mass NaHCO₃ in small-, medium-, and large-sized capsules. *a condition × time interaction between small and medium capsules, where p < 0.05. ∇a condition × time interaction between small and large capsules, where p < 0.05. ■a condition × time interaction between medium and large capsules, where p < 0.05.

Figure 2

Mean (±SD) and individual peak changes in blood bicarbonate concentration [${\text{HCO}}_3^{-}$] (ΔC_max) following the consumption of 0.3 g·kg⁻¹ body mass NaHCO₃ in small-, medium-, and large-sized capsules. Small markers represent individual responses, and large markers represent the mean data for each capsule condition. The X and Y whiskers represent the SD of the sample in each condition for time-to-peak [${\text{HCO}}_3^{-}$] (T_max and ΔC_max, respectively).

Figure 3

Mean (±SD) palatability scores following the consumption of 0.3 g·kg⁻¹ body mass NaHCO₃ in small-, medium-, and large-sized capsules.