Sodium Bicarbonate as a Lactic Acid Buffer

Written by Amelie Lane

Sodium bicarbonate has been used by athletes as a performance-enhancing supplement, particularly for short, high intensity efforts, such as 400m, 1500m and 3000m races in athletics or the Keirin in track cycling. Its primary benefit lies in its ability to buffer lactic acid in the muscles, helping to delay the onset of fatigue.

However, emerging research is showing that sodium bicarbonate can also have benefits for longer endurance events such as cross country races, the 10km, marathons distances and tour cycling, due to multiple lactate peaks in the blood occurring. The major lactate peaks arise from changes in pace, climbs, and sprints, such as into the finish, but also from microaccelerations such as turning corners (very rarely do people hold a truly even pace).

It’s important to recognise that even in longer-duration events, athletes frequently engage the anaerobic energy system, leading to lactate accumulation. This intermittent reliance on anaerobic metabolism explains why sodium bicarbonate can support endurance performance, by buffering excess acid and helping to maintain muscular function during intense phases of the race. Within this article we will explore how sodium bicarbonate acts as a lactate buffer and examine its practical applications for endurance athletes.

Lactate

During sustained anaerobic respiration, the production of lactic acid increases. As an acid (proton donor), lactic acid lowers the pH of blood plasma, which negatively impacts athletic performance. Specifically, the accumulation of hydrogen ions (H⁺) from lactic acid leads to a condition known as muscle acidosis, characterized by a decrease in pH.

Under normal conditions, human arterial blood has a pH of 7.4, this is slightly alkaline, but in muscle tissue it is typically 7.0 (McNaughton, et al., 2008). During exercise arterial blood pH can fall to 7.1, and in muscles, 6.8 (McNaughton, et al., 2008), indicating a shift toward a more acidic environment. This acidification disrupts the body’s internal balance (homeostasis) and compromises enzyme function critical to energy production. Sodium bicarbonate, a naturally alkaline compound, can help counteract this pH drop by acting as a buffer, neutralizing excess hydrogen ions and assisting in the restoration of optimal pH conditions for enzymatic activity.

Lactic acid can dissociate into two ions: Lactate (-) and Hydrogen ions (+). While lactate is often blamed for fatigue, it is the hydrogen ions that primarily cause problems by lowering pH. This acidic environment reduces the effectiveness of enzymes, particularly those involved in glycolysis, such as phosphofructokinase, ultimately impairing ATP production (Hussey, 2023). If pH deviates too far from the enzyme's optimum, these proteins may denature (no longer work), leading to a significant decline in energy output. Therefore glycolysis, the first part of respiration, cannot be catalysed and slows down significantly. As a result, this leads to a state of fatigue as less ATP is formed.

In addition to enzyme inhibition, excess hydrogen ions can impair muscle contraction by decreasing calcium ion sensitivity and interfering with cross-bridge cycling—both vital processes in muscular function (Grgic, 2021). Fatigue may also be exacerbated by the accumulation of other metabolites, such as potassium and phosphate ions, or by a depletion of energy substrates like glucose (McNaughton et al., 2016).

Interaction in the body

Sodium bicarbonate (NaHCO3) is an ionic compound (a salt). Therefore, when it is ingested, it enters the stomach and dissociates into sodium (Na⁺) and bicarbonate (HCO₃⁻) ions. This increase in bicarbonate concentration can raise pH, making the local environment more alkaline. Some of the bicarbonate reacts with hydrochloric acid (HCl) in the stomach via a typical acid-base neutralisation reaction:

Dissociation of salt: Na(HCO3)2↔Na++2HCO3-

Reaction in the Stomach: HCO3-+HCl →CO2+ H2O+Cl-

The HCO3- comes from ingestion of sodium bicarbonate and the HCl from stomach acid. The release of CO2 results in minor belching, a common side effect of supplementation.
Due to the protective gel technology developed by FLYCARB the majority sodium bicarbonate in BiCarrb does not react with the stomach acid. This allows it to reach the intestine where it is absorbed into blood via the villi. Once in the blood, it starts to act as a lactate buffer.

Mechanism of action and buffering

Once absorbed, the elevated concentration of bicarbonate in the blood induces a state known as metabolic alkalosis, where plasma pH rises and hydrogen ion (H⁺) concentration (McNaughton, et al., 2016). This shift creates a transmembrane concentration gradient between muscle cells and blood plasma.

While muscle cell membranes are impermeable to bicarbonate ions, they do allow hydrogen ions to diffuse. As a result, H⁺ ions move out of the muscle cells down the concentration gradient and into the intramuscular regions and blood plasma.

This efflux of H+ restores (or buffers) the acid base balance of the blood plasma, reducing the HCO3- concentration, and in turn acidosis in muscle cells through the removal of H+ ions. In essence, sodium bicarbonate buffers lactic acid by facilitating the removal of hydrogen ions from muscle tissue, thereby improving the cellular environment for energy production and reducing fatigue.

Buffering of Lactate

Lactate and bicarbonate react when they come into contact in the bloodstream, particularly during intense exercise, when lactate accumulates in muscle tissue as a by-product of anaerobic respiration When the body produces a strong acid such as lactic acid, it dissociates and donates a proton (McNaughton, et al., 2008), this is what makes it an ‘acid’. The H+ (proton) will be attracted to negative HCO3- ions and bind, forming H2CO3, known as carbonic acid. This then dissociates to form water and carbon dioxide, which eventually are excreted by the lungs. As a result, the hydrogen ion concentration is reduced, increasing blood pH and reducing acidosis. This reaction reduces the concentration of hydrogen ions in the blood, which helps to raise blood pH and counteract acidosis: H++HCO3- ↔ H2CO3 ↔ H2O+CO2

Conclusion: Smarter Buffering for Better Performance

Sodium bicarbonate has long been recognised as a powerful ergogenic aid, particularly for high-intensity and middle-distance athletic efforts. However, as evidence grows, it is increasingly clear that its buffering capabilities also benefit endurance athletes who face repeated bouts of anaerobic effort throughout longer events. Whether accelerating out of corners, surging up climbs, or sprinting to the finish, these micro-intensities cause spikes in lactate production and muscular acidosis. By neutralising excess hydrogen ions, bicarbonate helps maintain blood and muscle pH, supporting enzyme function and delaying fatigue. However, traditional forms often cause gastrointestinal discomfort due to early reaction in the stomach.

BiCarrb uses a protective gel technology to delivers sodium bicarbonate more efficiently to the intestine, enhancing absorption and minimising GI side effects. This enables athletes to gain the full buffering benefit.