As the world population grows, we have a pressing need to eat better and farm better, and those of us trying to figure out how to do those things have pointed at lots of different foods as problematic. Almonds, for their water use. Corn, for the monoculture. Beef, for its greenhouse gases. In each of those cases, there’s some truth in the finger-pointing, but none of them is a clear-cut villain. There’s one food, though, that has almost nothing going for it. It occupies precious crop acreage, requires fossil fuels to be shipped, refrigerated, around the world, and adds nothing...