Akicita, despite my telling this manufacturer for years that 4-AD is inherently tasteless and that the bitterness of their product is from impurities, they insisted I was not telling the truth and that 4-AD was “inherently bitter,” there were no impurities, I was lying etc.
However, now that there is better 4-AD from other manufacturers which is colorless and perfectly tasteless, the truth of what I said
is knowable to anyone who has tried using both types of 4-AD. And some have posted on this board that they have tried such 4-AD from other manufacturers and indeed it is colorless and tasteless, instead of being contaminated. (Also, assaying to much higher purity, like 98% vs 90%.)
So I would not assume their apparent assertion is true that the stomach pain problem is just inherent to 1-AD and not a result of a toxic impurity, especially lacking an analysis that accounts for 100.0% and their track record for impure products.
“Fool me once, shame on you, but fool me twice, shame on me,” is my motto on things like that.