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

in International Journal of Sport Nutrition and Exercise Metabolism
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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.

Carr and Gore are with the Physiology Dept., and Slater and Burke, the Sports Nutrition Dept., Australian Institute of Sport, Canberra, Australia. Dawson is with the School of Sport Science, Exercise and Health, The University of Western Australia, Perth, Australia.