While it be easy to say that the U.K. government wanted to keep citizens healthy so they could chuck more bodies into during World War II war machine, health was the stated goal. The Wartime Kitchen says that the National Loaf had extra vitamins and calcium in it, which was great for the poorest in society. Made from wholemeal flour — another term for whole wheat or whole grain — the National Loaf was far more healthy than white bread. Real Simple explains that white bread has the bran and germ removed (the parts with vitamins, proteins, oils, etc.), which leaves only the endosperm (the startchy bit). This means that white bread wastes flour because the bran and germ are removed, which makes it harder to feed everyone.
Per Historic UK, bakeries only had one day a week to bake their loaves, and couldn’t sell any till the following day. This would have proved troublesome for Brits, because as The Wartime Kitchen says, the National Loaf dried out rather quickly. The bread was already dry to begin with, had a grainy, “sawdust”-like texture, and a grayish color like its flour. In other words, folks found it generally unappetizing. It also contained a lot of salt so it would keep better. As for keeping the bread moist, folks just resorted to dunking it in water. And yes, this includes soldiers, per Pacific Atrocities, who also had the National Loaf shipped to them.
