I don't usually suffer heartburn unless I eat a few foods, namely oatmeal, whole wheat, peanut butter, any calcium supplements of any kind. So I avoid those when hiking/backpacking. But for some reason no matter what I eat, especially on a backpacking trip, as soon as I'm up and walking again the acid comes churning up like scalding lava. It sears my esophagus so badly that eating and drinking anything is very painful for a few days afterward. I try drinking lots and lots of water to try to dilute or tamp down the foods/acid but maybe that's making it worse? Next time I'll take Prilosec or something like that with me to see if that helps. I thought, the last couple of times out, that it was just a particular food that I ate, but I've changed up foods and it still happened this past weekend. I seem to be able to eat anything for dinner, lay down, and sleep just fine. It's breakfast and lunch that does it. I have wondered if it has something to do with my hip belt across my stomach, maybe it's pushing on me too much? Doesn't feel that tight, but that seems to be the only constant.