Food, by almost every measure imaginable, is getting cheaper, and increases in production have outstripped increases in population by wide margins. But first, the estimates for our global supplies of these things keep getting revised upward. Second, it really wouldn't be that big a problem. But more pragmatically, we can substitute things. If aluminum gets too expensive, buy paper.
Substitution is the great glitch which fouls up the math of worry warts.
If one commodity becomes too expensive, another commodity will do the trick. In the 19th century that wasn't true, but it is now, and that's why things are getting so good. We no longer use wood for fuel and our forests have grown back spectacularly. We now have more trees on the East coast than we did in the 19th century. By the mid 1990s, the United States had 128 million more acres of forest than it did in 1920.