Baking soda's main active ingredient, sodium bicarbonate, is most commonly used medicinally to treat acid reflux disease, explains Healthline. Although side effects are usually rare and not life-threatening, they can include nausea, bloating, gas and allergic reactions, according to WebMD.
Sodium bicarbonate may pose additional side effects that are more rare and more severe. These include swelling in the hands, feet or ankles; unusual weight gain; chest pain; seizures; dizziness; muscle aches and spasms; mood changes; vomiting; weakness; increased urination; and trouble breathing. Users who may have large doses of calcium present in their system are cautioned about the interaction of calcium with sodium bicarbonate to produce a condition known as milk-alkali syndrome, notes WebMD. Calcium can become concentrated in the body from various sources, including diet, supplements and other medications.
The use of sodium bicarbonate as an antacid is not recommended for those on a low-sodium diet, since it is a form of sodium. Sodium bicarbonate is naturally produced by the pancreas to neutralize stomach acids, notes Healthline. This production can be inhibited by unhealthy lifestyle choices such as smoking. In these instances, sodium bicarbonate may be used effectively to neutralize stomach acids and decrease esophageal damage from acid reflux disease.