I've been reading an apocalyptic book titled The End of Food, by Thomas F. Pawlick. It opens with the most startling information, which is that the nutritional value of most foods has been dropping over the last half-century. The theory underlying this set of facts is that industrial production of food seeks to maximize production, which leads to examples such as overuse of fertilizers (which makes the soil less rich) and grain-fed cows (which leads to lower-quality beef).
Overall, the book presents some interesting information, but I found it a little too over the top. It is somewhat unsurprising that "mass-produced" food is low quality: it will always be the case that the highest-quality food costs much more than many people can afford. I agree with the author that it is very short-sighted of our civilization to misuse natural resources in the way that we do, but all of these implicit decisions are driven by increasing populations.