Question

why do you think that carbonates are not digested in the stomach

Answer 1

we humans doesn't have that much of carbonates digestive enzymes so

Answer 2

Answer:

But the carbonation in seltzer, aka soda water or club soda, is the real culprit here. ... "You drink those, and the air builds up in your stomach, which can cause abdominal distention." In addition to causing bloating, drinking a lot of seltzer may result in a few other uncomfortable issues, too.