Some athletes consume sodium bicarbonate—also known as baking soda—hoping to neutralize the lactic acid that builds up in blood and muscles during intense exercise and thus causes fatigue and impairs performance.
Researchers have studied this proposed benefit of sodium bicarbonate for decades, for sprints as well as endurance events, with conflicting results. A 2008 review, for instance, noted performance benefits in both a 1,500-meter race and intermittent-sprint cycling, but not in a 600-meter run. A 2010 study found no benefit in elite rugby players in New Zealand—and in fact the side effects (notably bloating, cramps, diarrhea and nausea) may have impaired performance. Most recently, a small study of competitive college tennis players in Taiwan found that sodium bicarbonate did improve performance.
If sodium bicarbonate has any beneficial effect on performance, it’s minimal. Besides being high in sodium, it can cause gastrointestinal distress. If you have kidney problems, it can be dangerous. In rare cases, swallowing large amounts of sodium bicarbonate on a very full stomach could even result in stomach rupture.