I used to have horrid heartburn every night for many many years. Popped prylosec (sic?) constantly. I gave up anything processed when I started SBD 3 years ago. Discovered it was processed white flour that was doing it. When I stopped the white flour, the heartburn went away instantly and has never returned. Same with my husband. I eat only whole grains and no problem at all, so it's not really "carbs" per se, it's processed stuff. Lots' of chemicals and junk are added during the processing of flour like chlorine gas.
Read this and you can understand why your "insides burn".