My position on either dogfood OR soylent would be as follows: if people are obviously making an effort to contend that “x” particular ingredient is “not known to be harmful” to the species that’s ingesting it, well, what’s that all about? Ingredients of rations designed to provide complete balanced nutrition are not in there because they are not known to be harmful! So certain questions should be asked (and answered) concerning something like beet pulp when it turns up in a formulated ration. (1) Is this ingredient known to be a foodstuff which the species in question would naturally and normally eat, i.e. part of the diet under which the species evolved? (2) If not, then why is it included in the ration? (3) If the answer to (2) is “because it’s cheap, easy and available,” then has that ingredient been subjected to close and scrupulous examination and testing? and (4) Has it been proven to be nutritious and healthful for this species? Now, if the answer to (4) is not strongly affirmative, then whoever formulated the ration stands at risk of being presumed to be acting primarily for profit-motive, to the disregard and probably the detriment of good nutrition.
The fact that there are massive numbers of products out there that come off looking pretty shady by the above standards, does not excuse anyone. Just recently we’ve had an epidemic of nasty rail disasters, killing distressing numbers of people with each event. I don’t know whether the owners and operators of those rail companies will ever be formally charged with reckless endangerment of the public. Probably not, because making a goddamned buck is such a sacred goal in western society that it easily excuses even murder. But I’ll unhesitatingly say that the food companies that formulate and sell products that are likely to do harm to the consumer seem to be to be, even more than the rail operators, guilty of reckless endangerment.
Tl;dr - I don’t care a hang who thinks saponins have not been proven harmful to dogs. Can you show me a scientific study that says Drano is harmful to dogs? If you cannot – and let’s have it right now, we’re in a hurry – then am I justified in selling dogfood with a large dose of sodium hydroxide in it? Where is the evidence that dogs have any nutritional need of sodium hydroxide? And where is the evidence that they need saponins, or beet pulp? And if there is no such evidence, then why in blazes do so many kibble formulations include it?