The science of nutrition had become an important weapon for socially aware people in British society at the beginning of the twentieth century. At one end of the political spectrum were those concerned with imperial defence whose interests lay in the health and strength of the British soldier. At the other end were public health reformers investigating the ‘social problem’ for whom the social costs of urban–industrial society were to be found in terms of mortality and morbidity among women and children. Both were interested in physical standards and looked for guidance to the sciences of physiology and nutrition. Nutrition was still imperfectly understood. ‘Until 1900 energy dominated the science of nutrition’, wrote Professor V. H. Mottram and prior to the First World War, all dietaries emphasized the importance of the energy value of foods eaten. It had been known for much of the second half of the nineteenth century that food was composed of carbohydrates, proteins (or proteids as they were then termed) and fats. The energy required for daily needs had been estimated by Lyon Playfair as early as 1865, and later work by Pettenkofer and Voit in Munich, Rubner in Berlin and Atwater in the USA had made little difference to the view that adult males required between 2,700 and 4,500kcal per day according to the amount of physical effort their work required. By the beginning of the twentieth century these estimates were used by various authorities to limit the amount of food provided by institutional diets. In Britain, B. S. Rowntree was familiar with Atwater's work and used it in his study of workhouse diets. Institutional diets frequently ignored people's normal choices of food in favour of some combination of foods that expressed a social or moral prescription; for example, it was common for workhouse diets to allow adults no sugar or butter to prevent gratifying the inmates’ taste. Besides, from the point of view of economy, energy was obtainable far more cheaply from cereals if served as bread or porridge. For people at work, particularly when engaged in moderate or heavy manual work, animal food was thought to be essential. By 1900, protein was known to be an important component of the diet in building muscle as well as a source of energy.