Sodium bicarbonate, commonly known as bicarbonate of soda, is a chemical compound most people would associate with baking or cleaning. However, it is increasingly being used as a legal supplement by elite athletes, particularly runners, to improve their performance.
The compound has been described as a game-changer by those who use it, including the UK’s Keely Hodgkinson, who won the 800m gold at this year’s Olympic Games in Paris.
But does it actually work, and if so, how? And, importantly, are there any side effects?
How long has sodium bicarbonate been explored as a performance enhancing aid?
The effects of sodium bicarbonate on exercise performance have been explored since the 1930s. However, it wasn’t until the 1980s that the effects of the compound on exercise performance began to receive international attention.
Since then, many studies have explored the effects of sodium bicarbonate on performance in various sporting disciplines, from combat sports to high intensity running and swimming, making it one of the most well-researched supplements used in sport.
How does it work?
There is not yet an agreed consensus on exactly how sodium bicarbonate enhances performance, but it is likely that the mechanism lies in its role in supporting extracellular buffering capacity.
Blood bicarbonate (HCO3-) is part of the acid–base buffer system that helps to regulate blood pH concentrations and supporting metabolic functions. If blood pH is too alkaline a proton dissolves from carbonic acid (H2CO3) forming HCO3-.
If the blood pH is too acidic, HCO3- binds a proton to form H2CO3, which then dissociates into water and carbon dioxide (CO2). This leads to increased breathing rate in order to release more CO2 and restore the acid–base balance.
The additional buffering capacity provided by a bicarbonate supplement has been found to increase blood lactate after exercise, which is suspected to be due to a greater flow of hydrogen ions out of muscle tissue. This reduces the build-up of lactic acid in the muscles and overall fatigue.
Who uses it?
Sodium bicarbonate tends to be taken by track athletes, that is, competitors in disciplines that are high-intensity and take 1–15 minutes to complete, as it is for this window that there is the most evidence of improved performance. For example, it has been reported that sodium bicarbonate was used by athletes competing at the 2024 Olympics including 800m Olympic champion, Keely Hodgkinson.
However, sodium bicarbonate is also used by many cyclists who compete in longer events, but whose power output varies during the course – meaning they may have periods of high intensity that match the duration for which sodium bicarbonate could be effective. It has also been reportedly used in professional long-distance running, for example, by Kílian Jornet Burgada, who has won some of the world’s most prestigious ultramarathons.
How do athletes take it?
The easiest way to take it is in powder form – available in any grocery store. But this brings issues around taste and gastrointestinal problems.
Some years ago researchers worked out that you could minimise the gastrointestinal problems by ingesting sodium bicarbonate in enteric-coated capsules that do not break down in the stomach but only later in the intestines, but this never really gained popularity.
Now use has increased since leading Swedish sports nutrition company, Maurten, released its ‘Bicarb System’ which promises all the benefits of sodium bicarbonate without the gastrointestinal upset. In this system mini bicarbonate tablets are encased in a hydrogel that slows their release. The company notes that the system must be swallowed and not chewed.
What is the dosage?
Studies suggest that sodium bicarbonate doses ranging from 0.2 to 0.5g per kilogram of bodyweight improve performance in endurance activities, including combat sports like boxing and wrestling, and in high-intensity cycling, running, swimming and rowing.
The time it takes for bicarb levels in the blood to peak varies between individuals, but is typically 1–3 hours after ingestion. Elite athletes often have this measured in training and then applied in races, but in general, it is taken 60–90 minutes before an event.
Some athletes may also take multiple-day protocols between three and seven days before the exercise and it is suggested that this could reduce the risk of bicarbonate-induced side effects on the day of competition. However, there is no evidence that adding bicarbonate for multiple days would have any additional benefit on performance. In cycling, athletes often take top-up doses of 5g every 1–2 hours in long races.
It has been suggested that long-term use of sodium bicarbonate, for example, before every exercise training session, may enhance training adaptations, such as increased time to fatigue and power output but again there is little evidence to support this.
How much does it improve performance?
In studies, supplementation with sodium bicarbonate has been shown to improve athletic performance by 1–3%. However, for the average athlete it is unlikely that the supplement would provide any real benefit. For elite athletes it is likely bicarb improves performance, but probably not to the extent shown in the studies: experts tell Chemistry World that if findings from trial settings were extrapolated in real events, you would expect to see a massive difference between those using the supplement and those who don’t – however, there is little evidence yet to show this.
Are there any side effects?
The incidence and severity of side effects vary between and within individuals. The most common side effects of sodium bicarbonate supplements include bloating, nausea, vomiting, and abdominal pain. This may be because the bicarbonate buffer system in the body is not solely responsible for blood pH but also serves other purposes like neutralising gastric acid in the stomach and duodenum.
The bigger problem is that a high intake of sodium increases the potential for water retention the next day and potentially high blood pressure. Many athletes report headaches after using it and the next day their weight can temporarily increase by up to 1kg. Nutrition experts usually advise athletes not to use it more than two or three times a week.
Ingesting sodium bicarbonate in smaller doses alongside a high-carbohydrate meal or in enteric-coated capsules can help reduce the likelihood of side effects.
Acknowledgment: With thanks to Tim Podlogar, a research fellow in sport, exercise and rehabilitation sciences at the University of Birmingham.
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