There has been a raft of "research" over the last ~decade that purports to show that poverty causes stupidity. My impression (as a scientist, kinda related area) is that it's been discredited.

You must draw the distinction between correlational evidence (what this submission is doing) and causal claims, which is what most of the research you're pointing to makes.

TL;DR: Poverty doesn't cause lower intelligence. Catastrophically bad diet (to the point of stunting) will, though, in ref to your 2008 link. 2008 study is very weak and doesn't look at starvation, only correlational, they find a very small effect and it's very likely some unmeasured confounds.