Does varying the ingestion period of sodium citrate influence blood alkalosis and gastrointestinal symptoms?

Abstract

Objectives: To compare blood alkalosis, gastrointestinal symptoms and indicators of strong ion difference after ingestion of 500 mg.kg-1 BM sodium citrate over four different periods.

Methods: Sixteen healthy and active participants ingested 500 mg.kg-1 BM sodium citrate in gelatine capsules over a 15, 30, 45 or 60 min period using a randomized cross-over experimental design. Gastrointestinal symptoms questionnaires and venous blood samples were collected before ingestion, immediately post-ingestion, and every 30 min for 480 min post-ingestion. Blood samples were analysed for blood pH, [HCO3-], [Na+], [Cl-] and plasma [citrate]. Linear mixed models were used to estimate the effect of the ingestion protocols.

Results: For all treatments, blood [HCO3-] was significantly elevated above baseline for the entire 480 min post-ingestion period, and peak occurred 180 min post-ingestion. Blood [HCO3-] and pH were significantly elevated above baseline and not significantly below the peak between 150-270 min post-ingestion. Furthermore, blood pH and [HCO3-] were significantly lower for the 60 min ingestion period when compared to the other treatments. Gastrointestinal symptoms were minor for all treatments; the mean total session symptoms ratings (all times summed together) were between 9.8 and 11.6 from a maximum possible rating of 720.

Conclusion: Based on the findings of this investigation, sodium citrate should be ingested over a period of less than 60 min (15, 30 or 45 min), and completed 150-270 min before exercise.

Fig 1. Blood pH and blood [HCO₃^-] after 500 mg.kg^-1 BM sodium citrate ingestion.

(A) Blood pH irrespective of ingestion period (n = 16 participants, 4 sessions per participant, 64 total observations). (B) Blood pH following the completion of ingestion of sodium citrate over 15, 30, 45 or 60 min (n = 16 participants per ingestion period). (C) Blood [HCO₃^-] (mmol.L^-1) irrespective of ingestion period (n = 16 participants, 4 sessions per participant, 64 total observations). (D) Blood [HCO₃^-] (mmol.L^-1) following the completion of ingestion of sodium citrate over 15, 30, 45 or 60 min (n = 16 participants per ingestion period). (E) Delta blood [HCO₃^-] (mmol.L^-1) irrespective of ingestion period (n = 16 participants, 4 sessions per participant, 64 total observations). Values are mean and 95% confidence intervals. Zero (0) value on the x-axis corresponds to the completion of sodium citrate ingestion. Grey (shaded) area in (E) indicates 6 mmol.L^-1 above baseline. * elevated (p < 0.05) compared to baseline. ^# time interval where values are above baseline (p < 0.05) and not below gPeak (the maximum mean value, as ascertained from cumulative group data; p > 0.05).

Fig 2. Blood [Na⁺], blood [Cl^-] and plasma [citrate] after 500 mg.kg^-1 BM sodium citrate ingestion.

(A) Blood [Na⁺] (mmol.L^-1) irrespective of ingestion period (n = 16 participants, 4 sessions per participant, 64 total observations). (B) Blood [Na⁺] (mmol.L^-1) following the completion of ingestion of sodium citrate over 15, 30, 45 or 60 min (n = 16 participants per ingestion period). (C) Blood [Cl^-] (mmol.L^-1) irrespective of ingestion period (n = 16 participants, 4 sessions per participant, 64 total observations). (D) Blood [Cl^-] (mmol.L^-1) following the completion of ingestion of sodium citrate over 15, 30, 45 or 60 min (n = 16 participants per ingestion period). (E) Plasma [citrate] (μmol.L^-1) following the completion of ingestion of sodium citrate over 15, 30, 45 or 60 min (n = 16 participants per ingestion period). Values are mean and 95% confidence intervals. Zero (0) value on the x-axis corresponds to the completion of sodium citrate ingestion. * elevated (p < 0.05) compared to baseline. ^# time interval where values are above baseline (p < 0.05) and not below gPeak (the maximum mean value, as ascertained from cumulative group data; p > 0.05). ^$ difference (p < 0.05) between 15 min all other ingestion periods. ^@ difference (p < 0.05) between 15 min and 45 min ingestion period. ^{^} difference (p < 0.05) between 15 min and 60 min ingestion period. gPeak for blood [Na⁺] occurred 120 min post-ingestion (A), gMin occurred 270 min post-ingestion for blood [Cl^-] (C).

Fig 3. Gastrointestinal symptoms after 500 mg.kg^-1 BM sodium citrate ingestion.

(A) Mean and range of gastrointestinal symptoms (rating) following completion of ingestion of sodium citrate, with a maximum possible rating of 40 at each time-point, irrespective of ingestion period (n = 16 participants, 4 sessions per participant, 64 total observations). (B) Mean and range of gastrointestinal symptoms (rating) following completion of ingestion of sodium citrate over 15, 30, 45 or 60 min, with a maximum possible rating of 40 at each time-point (n = 16 participants per ingestion period). (C) Frequency of each gastrointestinal symptom reported by all participants after ingestion of sodium citrate over 15, 30, 45 or 60 min (n = 16 participants). For both (A) and (B), zero (0) value on the x-axis corresponds to the completion of sodium citrate ingestion.