Sodium
bicarbonate

It is the same compound as baking soda, NaHCO₃: the white powder that makes cakes rise. Chemically there is no separate sports version.

Your body already makes it and circulates it in the blood, where it is one of the central pieces of the system that keeps the body’s pH stable. Taking it in quantity raises blood bicarbonate for a few hours, and it is precisely in that rise that its whole effect lies.

It is not a stimulant and, with preserved kidney function, it does not accumulate: there is no need to take it daily. Nor do you feel anything when you swallow it, beyond the salty taste and, sometimes, its effects on the stomach.

During a very intense effort, the muscle generates hydrogen ions faster than it can get rid of them, and that build-up is part of why you have to ease off the pace. The extra bicarbonate circulating in the blood helps draw those ions out of the muscle.

The improvement measured is small: meta-analyses place it between 2 and 3% in high-intensity exercise. In an event decided by tenths of a second, that counts; in any ordinary training session, you will not notice it.

The Australian Institute of Sport classifies it in Group A, its category of solid scientific evidence for specific sporting uses with established protocols.

Its territory is high-intensity efforts lasting between 30 seconds and 10 minutes, such as the 100 and 200 meter swim, the 2,000 meter row, middle-distance running or track cycling. It can also be useful in combat, team and racket sports, where intense bursts are repeated with short rests.

Outside that window the backing blurs. In a ten-second sprint, the effort ends before acidity gets to be the problem; in a long race at a sustained pace, the limit is a different one: fuel and oxygen.

In an audit of the published studies on bicarbonate, only 4% had been done with women participants. The little that has been published points in the same direction, but it is too little to claim that the response is the same.

The protocols with backing use between 0.2 and 0.4 grams per kilo of body weight — 0.3 g/kg, the midpoint of the range, is about 21 grams for someone of 70 kg — taken 120 to 150 minutes before the effort and together with a carbohydrate-rich meal.

Three details of those protocols change the experience a great deal: splitting the intake over 30 to 60 minutes instead of swallowing it all at once, taking it with food, and drinking around 10 milliliters of fluid per kilo of body weight, because without enough fluid the bicarbonate drags water into the intestine.

There is also a multi-day protocol, with the daily dose split between meals for up to five days before competing. In the studies, that protocol is associated with fewer digestive problems on competition day.

The AIS is explicit on one point: the protocol is tried out in training, several times, before being taken to a competition.

Nausea, abdominal pain, bloating, diarrhea and vomiting. It is the factor that decides whether bicarbonate serves you or ruins your day, and it is not a rarity.

In the continuous running trials, digestive symptoms appeared in 29.5% of those who took bicarbonate versus 2.6% with placebo, and 8.7% dropped out of the study for that reason, versus 1.6% in the placebo group.

It is not just discomfort. When it appears in competition, the studies describe that it can erase that 2 or 3% improvement and leave whoever takes it below where they would have been had they taken nothing.

The strategies for reducing it have backing — capsules instead of dissolved powder, enteric-coated capsules, hydrogel systems, lower doses or the multi-day protocol — but none of them eliminates it for everyone.

Outside sport, the uses of bicarbonate backed by clinical trial are medical and supervised: correcting the acidity of the blood in some kidney diseases and alkalinizing the urine in specific situations. They are treatments that a professional prescribes and monitors.

As a home antacid it is very widespread and there are barely any trials that back it. What is documented are its risks, and the main one goes unnoticed easily: a sporting dose of 21 grams supplies about 5.75 grams of sodium, almost three times the daily maximum the WHO recommends.

Sodium bicarbonate does not appear on the World Anti-Doping Agency’s list of prohibited substances. Each federation and each national body also has its own rules.

It does have one little-known practical consequence: taking it alters the pH of the urine, which can take several hours to return to the values that anti-doping controls accept. It is not a positive, but it can upset the routine of an athlete who happens to be tested that day.

The sodium load is the first reason not to take it on your own. The prudent thing is to discuss it with a professional in cases of hypertension, heart failure, kidney disease or any indication to restrict salt, and also during pregnancy and breastfeeding, where information is lacking.

All the protocols described come from studies carried out in adults. No evidence has been located on the use of bicarbonate in minors, nor any specific protocols for them.

There is a second reason, less obvious. By modifying the acidity of the stomach and of the urine, bicarbonate alters the absorption or the elimination of several medications; some official prescribing documents name it expressly. Anyone who takes medication regularly has a conversation there that is worth having with their doctor or their pharmacist.

A note about doses: the serious published cases come from intakes far above the sporting ones, sustained for weeks or massive all at once. Above the range the studies work with there are no data of additional benefit, and digestive symptoms increase with the dose.