For food, it depends on how scientific we want to get. My generous ruling would be that the conjured food would be real until it expired, which would mean that all of those human tissues which had been bolstered and renewed by conjured food would suddenly have holes: first filled with ectoplasm, and then nothing. Probably not fatal, though it would be like using hydrogenated oil, but it would have lost any nutritive advantage. Depending on how long it lasted, the consumer may not even feel hungry suddenly, but there might be some sort of general malaise.
That said, we renew our cellular materials completely every 5 years or so, IIRC, so theoretically, if someone set up the ritual to last for "a few years" or "a decade," that food would, as far as I am concerned, be nutritive and whole for human consumption, and the individual components will have been fully used and recycled out of the body before it expires into ectoplasmic goo somewhere else.
I think the stomach acid issue is an important consideration, and may mean that even this generous interpretation wouldn't be feasible.
I wouldn't allow conjured versions of real-world items to satisfy a Catch. However, this brings up a good question: could some Catches be designed to *require* conjured substances to be satisfied?
