Henry Hobhouse’s book Seeds of Change: Five Plants That Transformed Mankind (now six, with the addition of cacao) contains the remarkable fact that at the height of the slave trade a single teaspoon of sugar cost six minutes of a man’s life to produce. Reason enough to cheer the abolition of slavery, I suppose. But that doesn’t mean that everything is sweetness and light in the business of sugar. Or salt. A photo gallery in The Big Picture made that very clear, and inspired Rachel Laudan, a food historian, to write in praise of industrial salt and sugar.