There is good Aristotelian reason to think that when a particle accretes to a substance--say, when I eat it--the particle ceases to exist. For prior to being accreted, it seems the particle is an independent substance. But a substance can't have substances as parts. And it seems absurd to think that the particle would change from being a substance to a non-substance.
But the view that post-accretion the object that is now a part of the substance is distinct from the object that was accreted is counterintuitive. Here I want to run a partners in crime response to this by showing how a very different and yet fairly mainstream set of assumptions leads to the same counterintuitive conclusion. This should help make that conclusion a little less counterintuitive.
To that end, assume reality is four-dimensional, that objects have lots of temporal parts and that parthood is transitive. This is a fairly commonly accepted set of assumptions. Now suppose I ate a particle x. I will argue that the particle perished in the process. For suppose that x is still a part of me. Let u be a temporal part of x prior to the accretion. Then x is a part of me. But u is a part of x. So by transitivity of parthood, u is a part of me. But that's absurd. So we must deny that x is a part of me on this set of assumptions, too. Hence, this set of assumptions leads to the same conclusion that it is impossible for an object to exist as not a part of something and then continue to exist as a part of that object.