Effect of Sodium Bicarbonate on [HCO3−], pH, and Gastrointestinal Symptoms

Abstract

Context:

Sodium bicarbonate (NaHCO ₃) 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 NaHCO ₃ with sodium citrate (Na ₃C ₆H ₅O ₇), and coingested food and fluid.

Purpose:

To quantify the effect of ingesting 0.3 g/kg NaHCO ₃ on blood pH, [HCO ₃−], 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 NaHCO ₃ experimental ingestion protocols and 1 placebo protocol. Capillary blood was taken every 30 min and analyzed for pH and [HCO ₃−]. 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:

[HCO ₃−] and pH were substantially greater than in placebo for all other ingestion protocols at almost all time points. When NaHCO ₃ was coingested with food, the greatest [HCO ₃−] (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 NaHCO ₃ solution.

Conclusions:

The changes in pH and [HCO ₃−] for the 8 NaHCO ₃-ingestion protocols were similar, so an optimal protocol cannot be recommended. However, the results suggest that NaHCO ₃ coingested with a high-carbohydrate meal should be taken 120–150 min before exercise to induce substantial blood alkalosis and reduce GI symptoms.