They betrayed their presence through illnesses befalling groups of people who for one reason or another were deprived of one of them. The prevalence of scurvy, which results from a deficiency of vitamin C, might well have started the process of discovering the vitamins. But scurvy was a special problem that arose mainly on long sea voyages and seldom affected the population at large. In general it would be true to say that most people in Europe, up to the 19th century, obtained what vitamins they needed from their diets, even if these diets were rather monotonous. However, the advent of processed foods in the 19th century brought with it, along with some advantages, new risks of vitamin deficiency, and set the stage for serious and systematic work on the causes of such deficiency diseases as beriberi and pellagra.