You would also have to wean us off meat, including poultry. Not all meat, sure, but the bulk is cereal-fed in CAFO factory operations. Similarly you'd have to wean us off most of the dairy produce and dairy-derived food we like, because grass-fed is not going to produce the quantities we've grown accustomed to. Then you'd have to wean us off bread and beer, and a whole host of extracted starches and sugars that are used in manufacturing much of the so-called processed foods. Because that's where most of the cereals are going.

So... most of humanity on a more-or-less vegan diet.