Is Individualization of Sodium Bicarbonate Ingestion Based on Time to Peak Necessary?

Abstract

Purpose To describe the reliability of blood bicarbonate pharmacokinetics in response to sodium bicarbonate (SB) supplementation across multiple occasions and assess, using putative thresholds, whether individual variation indicated a need for individualized ingestion timings. Methods Thirteen men (age 27 ± 5 yr; body mass [BM], 77.4 ± 10.5 kg; height, 1.75 ± 0.06 m) ingested 0.3 g·kg⁻¹ BM SB in gelatine capsules on three occasions. One hour after a standardized meal, venous blood was obtained before and every 10 min after ingestion for 3 h, then every 20 min for a further hour. Time to peak (T_max), absolute peak (C_max), absolute peak change (∆C_max), and area under the curve were analyzed using mixed models, intraclass correlation coefficient, coefficient of variation and typical error. Individual variation in pharmacokinetic responses was assessed using Bayesian simulation with multilevel models with random intercepts. Results No significant differences between sessions were shown for blood bicarbonate regarding C_max, ∆C_max or area under the curve (P > 0.05), although T_max occurred earlier in SB2 (127 ± 36 min) than in SB1 (169 ± 54 min, P = 0.0088) and SB3 (159 ± 42 min, P = 0.05). Intraclass correlation coefficient, coefficient of variation, and typical error showed moderate to poor reliability. Bayesian modeling estimated that >80% of individuals from the population experience elevated blood bicarbonate levels above +5 mmol·L⁻¹ between 75 and 240 min after ingestion, and between 90 and 225 min above +6 mmol·L⁻¹. Conclusions Assessing SB supplementation using discrete values showed only moderate reliability at the group level, and poor reliability at the individual level, whereas T_max was not reproducible. However, when analyzed as modeled curves, a 0.3-g·kg⁻¹ BM dose was shown to create a long-lasting window of ergogenic potential, challenging the notion that SB ingestion individualized to time-to-peak is a necessary strategy, at least when SB is ingested in capsules.