Carr, A. J., Slater, G. J., Gore, C. J., Dawson, B., & Burke, L. M. (2009). Effect of sodium bicarbonate ingestion on HCO3-, Ph, and gastro-intestinal symptoms. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

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This study quantified the effect of ingesting sodium bicarbonate (NaHCO3) on blood pH, bicarbonate (HCO3-), and gastro-intestinal symptoms over the subsequent three hours using a range of ingestion protocols in an attempt to determine an optimal protocol. Physically-active Ss (N = 13) undertook eight sodium bicarbonate ingestions and one placebo protocol. Six protocols used either sodium bicarbonate capsules or powder (0.3g/kgBM), ingested with either a 7 or 14 ml/kgBM lowkilojoule cordial over either 30 or 60 minutes. The other three protocols were i) placebo (NaCl equimolar for sodium bicarbonate at 0.3 g/kgBM with 14 ml/kgBM of fluid ingested over 30 minutes), ii) sodium bicarbonate (0.3 g/kgBM) and sodium citrate (0.1 g/kgBM) in 14 ml/kgBM of fluid ingested over 30 minutes, and iii) sodium bicarbonate capsules co-ingested with food (1.5 gCHO/kgBM) over 30 minutes with 7 ml/kgBM of fluid. Capillary blood was taken every 30 minutes and analyzed for pH and bicarbonate. Gastro intestinal symptoms were quantified every 30 minutes via questionnaire.

Bicarbonate and pH were substantially greater than placebo for all ingestion protocols at almost all time points. The highest value and the greatest increase in bicarbonate were at 150 minutes post-ingestion for sodium bicarbonate capsules co-ingested over 30 minutes with 7 ml/kgBM fluid and the meal. This bicarbonate was substantially greater than the lowest value at 150 minutes, which occurred after ingesting the 14 ml/kgBM sodium bicarbonate-sodium citrate solution over 30 minutes. The peak pH and its greatest increase from baseline occurred at 120 minutes post-ingestion of 14 ml/kgBM sodium bicarbonate solution over 60 minutes. Those values were substantially different to the lowest value recorded after the sodium bicarbonate-sodium citrate solution. Overall, there were minor differences in pH and bicarbonate between the eight protocols. The greatest incidence of gastro-intestinal side effects was at 90 minutes post-ingestion of 7 ml/kgBM sodium bicarbonate over 30 minutes, and the least side effects were for sodium bicarbonate co-ingested with the meal.

Implication. Changes in pH and bicarbonate for the eight sodium bicarbonate ingestion protocols were similar, hence an optimal protocol cannot be recommended. It is suggested that sodium bicarbonate should be ingested 120-150 minutes prior to exercise to induce substantial blood alkalosis, and sodium bicarbonate co-ingested with a high-carbohydrate meal may reduce gastro-intestinal symptoms.

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