I believe the concern is the excess metabolites 4Y being the marker for inflammation, since tryptophan converts to niacin, as @charlie has mentioned that detoxing in an art form, so when supplementing niacin the caveat would be aware as to how much niacin that you are in taking through foods and include that in your calculations for supplementation. Dr Smith has expressed this as well, you need to do this under supervision not be as he says,”Willy nilly “ about it. To me that sounds like more hair, nail and blood sampling, perhaps including now this new factor as it could be a potential warning sign future problems.I get the impression they weren't supplementing, so there implicating the small amounts of niacin added to wheat and questioning fortification