The nutritional transition brought about profound changes in the nutrition of the European population in the 19th and 20th centuries. The predominant consumption of cereals gave way to kilocalorie-, protein-, vitamin- and mineral-rich diets that involved a greater intake of animal products. However, not all population groups underwent this transition at the same pace; socio-economic conditions, sex and age led to important inequalities. This article uses institutional sources to analyse the nutrition of children during the early stages of the nutritional transition and to compare it with that of other age groups (adult psychiatric patients). The study examines the average diets and nutritional balance of foundlings in the Hospital General de Valencia from 1852 to 1931. The main conclusion of the study is that, throughout the period under study, foundlings were exposed to a poor, traditional diet, characterized by structural deficits and imbalances. This may have affected their physical growth, health and biological wellbeing in adulthood, and demonstrates that the nutritional transition was anything but a homogeneous process.