Do you need many different kind of proteins in your diet? I've heard people claim isolates are bad because of this - e.g. if you're eating whey you also need to eat casein.

I don't have much money and I'm on an extreme diet, so I feel like I need a solid source of protein for health (only concerned about heart and brain, not a bodybuilder). I'm looking at getting beef protein isolate, because it's super cheap. I can't tell if the stuff I'm reading online is just fear mongering or not.