Gastrointestinal Symptoms Associated With Sodium Bicarbonate Supplementation Protocols: A Systematic Review

Sodium bicarbonate positively impacts performance, but its associated gastrointestinal symptoms (GIS) may limit use. This systematic review synthesized literature that has evaluated GIS with sodium bicarbonate supplementation. Literature searches were performed from February 2024-March 2026. Eligible studies provided ≥ 5 g of sodium bicarbonate within a 24-h period or, if a multi-day protocol, at least one day involving ≥ 5 g. Included studies had a placebo group/condition or a comparison group/condition that created a contrast related to delivery method, form, or dose. In total, 101 investigations were summarized in six categories: acute single dosing (n = 35); acute spread dosing (n = 28); chronic dosing (n = 7); acute versus chronic dosing (n = 5); delivery form (n = 18); and other (n = 8). Existing literature suggests that common acute doses (0.2-0.4 g/kg) elicit mild-to-severe GIS, which likely increase in a dose-dependent manner when sodium bicarbonate is ingested in a single dose. Strategies to reduce GIS with acute dosing include spreading intake over hours, using enteric-coated capsules/tablets, and ingesting sodium bicarbonate mini-tablets within a carbohydrate hydrogel. Direct comparisons of these strategies to reduce GIS are absent in current literature; thus, ranking their effectiveness is not possible. Multi-day dosing may lessen GIS, but symptom documentation throughout supplementation periods is poorly characterized. Notably, 26 of 101 studies failed to perform inferential statistical testing to examine condition/group differences in GIS. Making definitive recommendations about sodium bicarbonate supplementation to minimize GIS remains challenging. Major needs remain for direct comparisons between protocols purported to reduce GIS and improvements in GIS data collection, reporting, and analysis.