Oh my dear Sam! You know you what you did 🙂 I don’t think your problem was baking powder but 6 slices in the short period on a first batch. You’ve been on the diet for a while now and it’s probably taking time for your body to adjust to it. I think I read somewhere that there is a recommendation to not have more than 3-4 slices per day, pretty positive it was Able who recommended this. Check the forum and see if you find a reason why.
I am in a country where listing ingredients is not that important. You buy a produce and nobody questions what’s in it, so none of the baking powder state if they are aluminum free or not. I just use it and have no reaction to it. Didn’t try baking soda at all.
I could not tolerate coconut bread so I had to introduce oat bran and buckwheat instead and I’m baking bread out of those two. To this day I am unsure if coconut bread was causing a die-off reaction or my stomach could not digest it. I tried it several times early in the treatment but then I never went back to test it again once I started to feel better. This new bread I bake is more similar to regular wheat bread to me than coconut one so I am lazy to change it.
Let us know how the second batch goes and slap yourself on the fingers if you go for it fourth time 🙂 Good luck!