Being serious for a moment, sadly that isn't true. Although it's a much bigger issue than food.
Sir Michael Marmot is currently leading a very detailed review of health inequalities - i.e. the gap between rich and poor. Saw a presentation by him with very persuasive data that showed that an intelligent child from a poor family will be overtaken by a dim child from a well-off family by age 10. Diet is presumably not the main issue there, but it was shocking to see the figures.
Nah, I know the poverty thing doesn't apply to Mr McQueen, that's why he remained incredibly bright despite the crap diet! (He's not alone in being fed carnation instead of formula/bm btw, very common in ye olden days - there was a thread here about it once. My dh was weaned on bones from the butcher, on the advice of the GP...)