Sweet stout (also called milk stout or cream stout) is a stout containing lactose, a sugar derived from milk. Because lactose is unfermentable by beer yeast, it adds sweetness, body, and calories to the finished beer. Milk stout was claimed to be nutritious, and was given to nursing mothers. In the period just after the Second World War when rationing was in place, the British government required brewers to remove the word "milk" from labels and adverts, and any imagery associated with milk.