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

Journal Title (Medline/Pubmed accepted abbreviation): Int J Sport Nutr Exerc Metab
Year: 2011
Volume: 21
Number: 3
Page numbers:189-194
doi (if applicable):

Summary of background and research design

Hypothesis: The authors did not state a specific hypothesis, but the purpose of the study was to examine several variables associated with the administration of sodium bicarbonate (e.g, fluid volume, capsules vs. solution, presence or absence of additional food, and ingestion period) to determine an administration protocol that would maximize the ergogenic effect while minimizing gastrointestinal symptoms.

Subjects: There were 13 recreationally active, healthy adults (8 female, 5 male; mean age 30 y, mean body mass 74 kg) who completed the protocol.

Experimental design: Randomized crossover

Treatments:A 300 mg/kg-dose of sodium bicarbonate (NaHCO3) was administered in 8 different ways to the subjects.  In one of the treatments, the above dose of NaHCO3 was delivered in combination with citrate (100 mg/kg) in a commercial product.  The placebo was equimolar sodium chloride (NaCl).

Protocol:The NaHCO3 dose was administered either in capsules or solution.  The fluid volume was either 7 or 14 mL/kg of water.  When the dose was administered with food, the meal was toasted bread with cereal bars (1.5 g carbohydrate/kg and ~544 kcal).  The ingestion period was typically 30 min, although it was allowed to vary to 60 min for two of the administrations.  There was at least 48 h separating the administration protocols.  Blood samples and gastrointestinal symptom ratings were collected at 30-min intervals for 3 h after the ingestion of the NaHCO3 was complete.  Blood samples (capillary finger stick) were analyzed immediately after collection for pH and [HCO3-].  Dietary intake was standardized among the treatments to eliminate the effect of variation in normal diet on acid-base status.  No exercise was performed during the tests.
Summary of research findings
  • All of the protocols resulted in higher pH and [HCO3-] than the placebo at virtually every time point.  The highest mean values for [HCO3-] and pH were 30.9 mmol/L and 7.49, respectively.  Values for both [HCO3-] and pH remained elevated above baseline throughout the 3 hour sampling period for all treatments.  Based on these data, the authors concluded that none of the protocols were superior to the others with respect to achieving the desired increase in these two variables prior to exercise.  However, the coadministration of NaHCO3 with citrate appeared to be somewhat less efficacious than the other treatments. 
  • Consuming the NaHCO3 in capsules, with a water volume of 7 mL/kg, and the meal over 30 min resulted in the lowest level of gastrointestinal symptoms.  The combination of NaHCO3 and citrate resulted in one of the higher intolerance symptom ratings.  However, the gastrointestinal symptoms reported during all the test protocols were quite similar to those reported for the placebo.
  • Based on the data presented above, the authors recommended that NaHCO3 be given alone, as opposed to with citrate.  Their general recommendation was to consume the NaHCO3 with food 120-150 min prior to commencing exercise.

Interpretation of findings/Key practice applications

This study answered several questions regarding the “optimal” administration of NaHCO3 for athletes.  The dose was fixed at 300 mg/kg based on previous work that has already established this dose (higher doses tend to cause more gastrointestinal distress).  The authors did not examine every potential combination, which would have been too labor intensive for the subjects to do in a crossover type study, but the study still provided useful data for those who wish to employ this technique.  The ability of all of these treatments to elevate both pH and [HCO3-] was consistent with many other reports in the literature.  There was no measurement of the effects of these administration protocols on actual exercise performance, but the ergogenic effect of bicarbonate loading has already been well documented in the literature.  For many athletes, the primary concern is not whether the technique works, but rather how it can be done so that gastrointestinal distress may be minimized.

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