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Sodium bicarbonate is a popular ergogenic aid in sport, with research on its potential to improve exercise performance stretching back several decades. But the side effects from ingestion can be, well, explosive. It can provoke nausea, bloating, cramping, and as previously described, diarrhea. Recently, a systematic review looked into why these symptoms arise and what strategies might reduce them. This article examines what the current research shows about sodium bicarbonate supplementation, the forms in which it is available, and the practical steps endurance athletes can take to minimize gastrointestinal distress while still capturing its performance benefits. We discuss this because sodium bicarbonate can meaningfully improve athletic performance, unless that is, you're stuck in a porta potty.
How it works
During moderate to high-intensity exercise, the body produces hydrogen ions faster than it can clear them. The resulting drop in muscle and blood pH is thought to be one of several factors limiting performance. Ingesting sodium bicarbonate raises blood bicarbonate concentration in a dose-dependent manner, increasing extracellular pH and delaying metabolic acidosis resulting from high-intensity exercise.This helps to delay fatigue.
Sodium bicarbonate doses of 0.2 to 0.5 grams per kilogram of body mass can improve performance in muscular endurance events, like high-intensity cycling, running, swimming, and rowing, with the strongest evidence for efforts lasting roughly 30 seconds to 12 minutes. Although primary evidence for its use lies in short-duration events, many endurance athletes use sodium bicarbonate for longer, steady-state events such as marathons, half- and full-distance triathlons, or ultra-distance races. For most endurance athletes, sodium bicarbonate is probably best thought of as a tool for the harder, shorter segments embedded within a longer event, such as a surge past threshold pace, a hard finish, or a demanding effort earlier in a race, rather than a strategy expected to improve steady-state pacing across an entire event.
Gastrointestinal symptoms, abbreviated GIS, are one of the most consistently reported drawbacks of sodium bicarbonate supplementation. When sodium bicarbonate reaches the stomach, it can react with hydrochloric acid to produce carbon dioxide, and when it reaches the intestines shifts extracellular fluid into the digestive tract due to an increased osmotic sodium load. This reaction is thought to be a major contributor to the bloating, cramping, nausea, and diarrhea that some athletes experience. It’s suggested a dose-dependent relationship exists between sodium bicarbonate and GIS, with direct comparisons showing that a 0.3 gram per kilogram dose tends to produce more frequent or more severe symptoms than a 0.2 gram per kilogram dose. The larger single doses, in the range of 0.4 to 0.5 grams per kilogram, are associated with substantial GIS in a large proportion of athletes. Even the smaller, minimally effective dose of 0.2 grams per kilogram is not risk-free. A meaningful minority of athletes will still report mild to moderate symptoms at this level.
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Method of Delivery
Because so much of the GIS risk stems from the interaction between bicarbonate and stomach acid, the form in which sodium bicarbonate is delivered has become an important area of research. Taking baking soda from your pantry and dissolving it in liquid is the least expensive option, costing roughly fifteen cents per dose, but it also tends to taste unpleasant and has been associated with more severe GIS than capsule-based alternatives. Standard gelatin capsules mask the taste but do not necessarily change how quickly the bicarbonate dissolves once it reaches the stomach. Delayed-release capsules appear to reduce GIS relative to gelatin capsules, though the amount of research on this particular format remains limited. Enteric coated capsules, designed to resist breakdown until they reach the small intestine, along with sodium bicarbonate mini tablets suspended in a hydrogel have both shown fairly consistent evidence of reduced GIS compared with traditional dosing. Again, this is likely because they limit the direct reaction between bicarbonate and hydrochloric acid in the stomach. At present, no study has directly compared enteric-coated capsules against the hydrogel bicarb system, so it is not yet possible to say which of these approaches works best for minimizing side effects. Pairing sodium bicarbonate with a meal or snack containing carbohydrate is another commonly used strategy that appears to reduce, though not eliminate, GIS. The findings suggest a pattern: the delivery methods of sodium bicarb have become quite effective at minimizing GIS, but this does not automatically translate into a guaranteed performance benefit, particularly for the sustained, moderate- to high-intensity efforts that make up most endurance events.
Timing
The timing and pattern of dosing has a meaningful effect on both efficacy and tolerability. For a single acute dose, the International Society of Sports Nutrition recommends ingestion 60 to 180 minutes before exercise or competition. Rather than consuming the full acute dose all at once, several studies have tested spreading a higher total dose, generally in the 0.4 to 0.6 gram per kilogram range, across multiple smaller doses over a window of thirty minutes up to nearly twenty hours before exercise. Taken together, this suggests that spreading a higher total dose across several hours may be a strategy that allows athletes to reach a larger total dose while keeping GIS manageable.
Multiple-day dosing takes a different approach, spreading smaller individual doses across three to seven days, with a typical total daily dose of 0.4 to 0.5 grams per kilogram divided into portions taken with meals. This approach appears to produce less GIS at the time of competition, likely because each individual dose is smaller and interacts with less stomach acid at once. It is worth noting, however, that most of these studies assessed GIS primarily around the time of the performance test at the end of the protocol, so how well athletes tolerate the loading days themselves, which could still affect training consistency, is not yet well understood. It’s important to note: this is a lot of sodium to take on across multiple days. For a 70kg athlete, 0.4g sodium bicarbonate per kilogram body weight equates to roughly 7700mg of sodium each day, for three to seven days. This is before accounting for the additional sodium consumed in regular food and meals.
What this means for Athletes
Altogether, this points to a few consistent themes worth carrying into practice. Gastrointestinal symptoms are common enough, and variable enough between individuals, that no athlete should assume they will tolerate a given dose, form, or timing simply because it worked for someone else. Athletes should weigh the potential performance benefit of sodium bicarbonate against the risk of gastrointestinal symptoms. They must establish their own individual tolerance and trial use during training. Whatever combination of dose, delivery method, and timing an athlete is considering, it should be tested repeatedly, under conditions that resemble race day as closely as possible, well before it is ever used in competition for the first time.
If you’re looking to sort out your race-day supplement strategy, the Fuelin coaches can help. While personalized supplementation regimens aren’t available in our program tiers, a nutrition consultation with one of the Fuelin coaches can help athletes figure out what’s right for them. A coach can guide athletes through testing strategies in training, tracking how the body responds, and fine-tuning a nutrition plan that holds up under race-day pressure. Sodium bicarbonate deserves the same careful, individualized approach as anything else before toeing the line, because the only sprint finish you want in a race is at the finish line, not to the porta potty.