Effect of sodium bicarbonate on [HCO3-], pH, and gastrointestinal symptoms

Int J Sport Nutr Exerc Metab. 2011 Jun;21(3):189-94. doi: 10.1123/ijsnem.21.3.189.


Context: Sodium bicarbonate (NaHCO₃) is often ingested at a dose of 0.3 g/kg body mass (BM), but ingestion protocols are inconsistent in terms of using solution or capsules, ingestion period, combining NaHCO₃ with sodium citrate (Na₃C₆H₅O₇), and coingested food and fluid.

Purpose: To quantify the effect of ingesting 0.3 g/kg NaHCO₃ on blood pH, [HCO₃-], and gastrointestinal (GI) symptoms over the subsequent 3 hr using a range of ingestion protocols and, thus, to determine an optimal protocol.

Methods: In a crossover design, 13 physically active subjects undertook 8 NaHCO₃ experimental ingestion protocols and 1 placebo protocol. Capillary blood was taken every 30 min and analyzed for pH and [HCO₃-]. GI symptoms were quantified every 30 min via questionnaire. Statistics used were pairwise comparisons between protocols; differences were interpreted in relation to smallest worthwhile changes for each variable. A likelihood of >75% was a substantial change.

Results: [HCO₃-] and pH were substantially greater than in placebo for all other ingestion protocols at almost all time points. When NaHCO3 was coingested with food, the greatest [HCO₃-] (30.9 mmol/kg) and pH (7.49) and lowest incidence of GI symptoms were observed. The greatest incidence of GI side effects was observed 90 min after ingestion of 0.3 g/kg NaHCO₃ solution.

Conclusions: The changes in pH and [HCO₃-] for the 8 NaHCO₃-ingestion protocols were similar, so an optimal protocol cannot be recommended. However, the results suggest that NaHCO₃ coingested with a high-carbohydrate meal should be taken 120-150 min before exercise to induce substantial blood alkalosis and reduce GI symptoms.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Citrates / blood
  • Citrates / pharmacology
  • Cross-Over Studies
  • Dietary Carbohydrates / administration & dosage
  • Drug Administration Schedule
  • Eating
  • Female
  • Gastrointestinal Diseases / chemically induced
  • Gastrointestinal Diseases / prevention & control*
  • Gastrointestinal Tract / drug effects*
  • Humans
  • Hydrogen-Ion Concentration / drug effects
  • Male
  • Sodium Bicarbonate / adverse effects
  • Sodium Bicarbonate / blood*
  • Sodium Bicarbonate / pharmacology*
  • Sodium Citrate
  • Surveys and Questionnaires
  • Time Factors


  • Citrates
  • Dietary Carbohydrates
  • Sodium Citrate
  • Sodium Bicarbonate