It seems that nuts that we harvest and crack ourselves are acceptable because that would limit our consumption.
This got me thinking about a simple criterion we can apply to what we eat. Perhaps we should asses everything we buy according to how it fits into feeding all of us.
We might think that meat, milk and fish are ok, so long as we do all the work of raising, slaughtering, butchering and cooking them. Few of us are prepared to do all that work and, if everyone did, we would need an extra couple of worlds to grow sufficient produce; so animal protein cannot possibly feed all us 7 billion.
The simple conclusion is that we can feed the world, and maintain a much higher level of vital good health, if we all stick to plant based whole foods.