Should you only eat food your great grandmother would recognize?

I've been reading the book White Bread: A Social History of the Store-Bought Loaf by Aaron Bobrow-Strain.  I'm only about a quarter of the way in, but so far it has been an informative take on some of the modern food debates seen through the history of white bread.  At times it falls into the big-is-bad or anything-for-profit-is-bad trap and often fails to fully appreciate the benefits of lower prices to the poor, but otherwise its an interesting read.  

I particularly liked the following passage:

At the start of the twenty-first century, a wave of neo-traditional food writers urged Americans to eschew anything “your great-grandmother wouldn’t recognize as food.” If your great-grandmother wouldn’t have eaten it, they argued, it wasn’t real food. This rule of thumb raised a few complications: I’m pretty sure my great-grandmother wouldn’t have recognized Ethiopian doro wat or Oaxacan huitlacochtle as anything a human would eat, and yet they’re two of my favorite foods. Neo-traditionalist’s dreams of “real” food have racial and nationalistic undertones, it seems. More importantly, they ignore the complexities and ambiguities of early twentieth-century American’s relation to food: which version of my great-grandmother’s bread am I supposed to reassure/ the laborious homemade one her husband demanded, or the factor-baked one she eventually came to love? Food writers selling a particular dream of “great-grandmother’s kitchen” rarely concern themselves with real people. What I want to know is how and why my great-grandmother’s generation came to desire the store-bought staff of life.