Athletic Performance and Kidney Health

Evidence Review

ISSN Position Stand (Grgic et al., 2021)

The International Society of Sports Nutrition conducted a comprehensive review of all available evidence on sodium bicarbonate and exercise, culminating in a formal position stand [1]. Synthesizing findings from multiple systematic reviews and meta-analyses, the ISSN concluded that supplementation at 0.2–0.5 g/kg improves performance in muscular endurance activities, high-intensity cycling, running, swimming, rowing, and combat sports including boxing, judo, karate, taekwondo, and wrestling. The ergogenic effects were most consistently demonstrated for exercise lasting 30 seconds to 12 minutes, though multi-bout exercise protocols and repeated-sprint formats also showed benefit. Critically, the position stand concluded that effects are present in both men and women, and noted that chronic pre-training supplementation may enhance training adaptations — including time to fatigue and power output — beyond the acute performance bump. GI side effects (bloating, nausea, vomiting, abdominal pain) were identified as the primary barrier to consistent use, with the recommendation that food co-ingestion and multi-day loading strategies substantially mitigate these issues.

Meta-Analysis of Athletic Performance (Peart et al., 2012)

This meta-analysis pooled randomized controlled trials examining sodium bicarbonate in trained versus recreationally trained athletes [2]. The overall effect size for performance improvement was moderate. A noteworthy finding was that specifically trained athletes showed significantly smaller effect sizes than recreational athletes — likely because trained athletes have more developed aerobic systems, higher natural buffering capacity, and greater tolerance for acidic environments. The study established practical protocol recommendations of 0.3 g/kg taken 60–90 minutes before exercise, which became the standard reference dose for subsequent research. The authors also noted that exercise type, duration, and intensity moderated the effect, with high-intensity anaerobic tasks showing the most consistent benefit.

Muscular Endurance vs. Strength (Grgic et al., 2020)

This systematic review and meta-analysis published in Sports Medicine focused specifically on separating the effects on muscular strength from those on muscular endurance [3]. The clear finding was that sodium bicarbonate supplementation acutely improved muscular endurance of both small (forearm, hand flexors) and large (quadriceps, whole-body) muscle groups, but showed no significant ergogenic effect on maximal muscular strength (tasks involving 1–3 repetitions to failure). This distinction makes mechanistic sense: maximal strength relies primarily on the phosphocreatine system and neuromuscular factors that are not limited by acid accumulation, while endurance under repeated or sustained contractions is directly impaired by hydrogen ion buildup. This meta-analysis helps practitioners identify the populations and training contexts where sodium bicarbonate will deliver the most value.

Foundational Anaerobic Meta-Analysis (Matson and Tran, 1993)

This early landmark meta-analysis examined 29 studies on sodium bicarbonate and anaerobic performance, reporting an overall effect size of 0.44 — a moderate-to-meaningful ergogenic effect [4]. At the time, individual studies showed inconsistent results, leading some researchers to dismiss bicarbonate as unreliable. The meta-analytic approach revealed that inconsistency stemmed largely from methodological differences: variation in dose, timing, exercise protocol, and failure to assess or control for GI discomfort all contributed to heterogeneous outcomes. The authors identified 0.3 g/kg as the threshold dose for consistent effects and established that timing (60–90 minutes before exercise) was critical for allowing blood bicarbonate to peak. This study built the evidentiary foundation for modern bicarbonate research protocols.

Landmark CKD Bicarbonate Trial (de Brito-Ashurst et al., 2009)

This randomized 2-year trial enrolled 134 adults with stage 4–5 chronic kidney disease and metabolic acidosis (serum bicarbonate 16–20 mEq/L) [5]. Participants received oral sodium bicarbonate (600 mg tablets three times daily, approximately 1.8 g/day) or standard care. The primary finding was striking: decline in creatinine clearance was 1.88 mL/min/1.73 m² per year in the bicarbonate group versus 5.93 mL/min/1.73 m² per year in controls — a roughly three-fold difference in progression rate. Patients in the bicarbonate arm were far less likely to experience rapid progression (9% vs. 45%; relative risk 0.15) and far less likely to progress to end-stage renal disease requiring dialysis (6.5% vs. 33%; relative risk 0.13). Nutritional parameters improved as well, with significant gains in lean body mass markers. Bicarbonate supplementation was well tolerated. This single-center trial established bicarbonate correction as a disease-modifying intervention in CKD management, not merely a symptomatic treatment.

UBI Study (Di Iorio et al., 2019)

The UBI Study was a larger open-label controlled trial enrolling 740 patients with CKD stages 3–5 and metabolic acidosis across multiple centers, randomized to bicarbonate treatment or standard care over 36 months [6]. Bicarbonate treatment significantly reduced the composite endpoint of creatinine doubling, all-cause mortality, and time to renal replacement therapy. The protective effect was most pronounced in patients with lower baseline serum bicarbonate, supporting a dose-response relationship between the degree of acidosis correction and nephroprotective benefit. In sub-analyses, bicarbonate treatment was also associated with reduced cardiovascular events, consistent with the known link between metabolic acidosis and cardiovascular risk in CKD. This larger, multicenter, real-world trial substantially strengthened confidence in the de Brito-Ashurst findings and has since informed updates to international nephrology guidelines recommending bicarbonate supplementation in CKD patients with confirmed metabolic acidosis.