MOST recipes aim at deliciousness. With nutraloaf (also spelt nutriloaf) the aim is to be as revolting as possible. It is made in prisons by baking leftovers and whatever else is to hand into a loaf, meeting minimum calorific and nutritional requirements. The ingredients vary. The Florida Department of Corrections recommends a basic mix of carrots and spinach, dried beans, vegetable oil, tomato paste, water, grits and oatmeal.

People who get past the smell describe the taste as bland. It looks like a lump of shredded, dried slop. One of the side effects is severe constipation. It is served three times daily without utensils, usually for no more than ten days as an extra punishment for prisoners who are already being held in isolation.

Prisoners, whose culinary expectations are already pretty low, often find it so disgusting that they stop eating for days rather than consume it. Decisions about its use are made capriciously, even by individual guards. Among the infractions it is most often used to punish are throwing food, spitting, making weapons and failing to obey an order.

Fewer prisoners are thought to be getting the stuff than heretofore, though it is hard to collate figures across America’s many prison systems. Institutions are not obliged to record or publish information on punishment meals. The constitution requires only that prisoners should receive food adequate to maintain health; it does not have to be tasty. Even so, nutraloaf has been scrapped by several states: California, Massachusetts, Minnesota, New York, Pennsylvania and, most recently, Maryland.

Inmates in several other states have challenged its use through the courts, mostly without success. “Plaintiffs all stated they refused to eat the meal loaf,” one court said in its ruling. “Thus, any weight loss cannot be attributed to a nutritional deficiency.”

Nutraloaf is obviously cheap. But it is probably a false economy. A sudden change in diet or going without food can seriously harm the health of prisoners with conditions such as diabetes. Depriving prisoners of decent food harms both individual and group morale—and has been known to cause riots. Restricting food should be used only as a last resort and then only for food-related misconduct, for short periods and under medical supervision, says David Fathi of the American Civil Liberties Union.

“This is OK. It’s not unconstitutional,” says Joe Arpaio, a former sheriff of Maricopa County, Arizona, as he picks over a lump of nutraloaf in a video from 2010. Mr Arpaio also dressed his prisoners in shaming pink underwear. Challenged to eat some nutraloaf, he sniffs, pulls a face, takes a little between thumb and forefinger, swallows and gags. “You know, quite frankly, I wouldn’t eat this,” he says. Nor should anyone else have to.