This paper addresses the question of dissemination of nutritional knowledge in textbooks of household schools between 1890 and 1940. It starts by considering the nature of food recommendations in manuals that are used in Belgian household schools, and then deals with the sources that are referred to by those who give food advice, comparing the latter to the state of the art of nutritional knowledge. If, prior to 1925, school manuals referred to working-class households, paid attention to abundant and economical food, recommended meat, hardly cared about breakfast and connected food to health in a general way, the manuals of the late 1920s and 1930s discussed the "average" consumer, advised limited meat consumption, warned against unbalanced diets that could lead to specific diseases and recommended required amounts of calories and vitamins. Textbook authors rarely referred to their sources--and if they did, international names were hardly mentioned--which raises the question of the value of the information in these textbooks. Yet from the late 1920s onwards, more direct references were made to science and researchers, which may be linked to the strengthening of scientific authority within society.