If the amino acid [gluten, l-glutamate] from China in pet food has been poisoned, should we assume that the amino acids that we get from China are safe? I can’t think of any amino acids that I have purchased that are not from China.
L-tryptophan, 1980’s, from Japan was contaminated and killed [mostly women] who used it. Contamination occurred from a new process, not adulteration.
You do not know the answer. But I don’t think that asking bulk nutrition would be productive either. Still, it is a question that should be asked.