They were a godsend to Europe in the 1500’s. They are very high in vitamin C and the shelf life of a potato is the longest of all C sources. In Northern Europe and Russia, the only source for C in the winter was pickled cabbage, i.e. sauerkraut. In Sweden alone, with a population of around 1 million in 1500 ce, 70,000 people died per year of scurvy and just about everybody else was sick by springtime. With the import of seed potatoes from the New World, that figure became negligible in just a few years. They keep extremely well in cellars, for up to three years, which means a good supply can get you through a winter or two after a couple of bad growing seasons in the days when that meant certain starvation.
It’s also an excellent source of sustained-release carbohydrate, meaning that one helping of potatoes the night before, would keep a field worker sustained throughout the next day in the days when peasants were forced to work from dawn to dusk. The energy that is not used, is easily stored as fat, which was extremely important as an insulator in the bitter winters of Northern Europe and Russia.
It was a wonder food to those people, for sure.