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

Sodium bicarbonate (NaHCO) 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 NaHCO 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. This study aims to determine the effects of NaHCO supplementation, administered in capsules of different sizes, on acid-base responses, GI symptoms, and palatability. 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 NaHCO/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 ([ ]) and potential hydrogen (pH). GI symptoms were measured using a questionnaire at the same timepoints, whereas palatability was recorded pre-consumption. Capsule size had a significant effect on lag time (the time [ ] changed, ) and the timing of peak blood [ ] ( ). Bicarbonate was significantly higher in the large-sized (28 ± 4 min) compared with the small-sized (13 ± 2 min) capsules ( = 0.009). Similarly, was significantly lower in the small capsule (94 ± 24 min) compared with both the medium-sized (141 ± 27 min; < 0.001) and the large-sized (121 ± 29 min; < 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 ( = 1.3, = 0.310). Similarly, capsule size had no effect on palatability ( = 0.8, = 0.409), with similar scores between different capsule sizes. Small capsule sizes led to quicker and of blood [ ] concentration compared to medium and large capsules, suggesting that individuals could supplement NaHCO in smaller capsules if they aim to increase extracellular buffering capacity more quickly.