It goes so much deeper than just bad food, its the modern environment in general which we simply cant get away from. Polution, poor quality food sources etc etc. We are inundated with toxins at ever turn and to a degree our bodies are designed to cope.
However what we have today is exacerbated by poorer and poorer food quality combined with more and more toxic exposure.
The only way we can really hope to cope at all, regardless of our food choices although admittedly for most this area can be improved, is with copiuos supplementation of what we need since its lacking in our food.