Soda or carbonated water is
water in which low levels of pressurized carbon dioxide has been dissolved,
thus creating carbonic acid. Soda water causes bloating, which stretches the
stomach. Mechanoreceptors in the stomach detect the stretching resulting in
parasympathetic innervations to gastrointestinal (GI) smooth muscles. This
results in an increase in GI motility.
Since soda water is in a liquid
form and thus easily passes down the oesophagus and the lower oesophageal
sphincter relaxes and opens to allow its entrance into the stomach. The upper
part of stomach relaxes to store the swallowed soda water. The digestive glands
in the stomach lining produce hydrochloric acid, containing pepsin. Stomach
mixes the digestive juices with soda water. Upon reaching the small intestine,
soda water mixes with secretions produced by the pancreas and liver.
When the stomach is empty, soda
water passes rapidly in to the duodenum where carbon dioxide is transformed
into bicarbonate. The carbon dioxide dissolved is rapidly released in gaseous
form as the fluid is warmed. The free carbon dioxide may be belched if the
expanding gas increases the pressure and stimulates the gastric fundus,
triggering the belching mechanism. Distention of gastric fundus can increase
transient lower oesophageal sphincter relaxation. If the soda water is taken
while or after eating it tends to localize in the upper part of stomach and
will produce feeling of fullness. Hence, carbonated water seems to influence
stomach function by both mechanical and chemical effects.
