This thesis explores how and why Health Foods – novel industrial foods that purportedly made more-or-less healthy adults healthier – became popular and culturally significant in Britain at the fin de siècle. I focus on several of the most advertised and, by implication, popular Health Foods, specifically meat extracts (Bovril), so-called pure cocoas (Cadbury’s and Sandow’s), products containing coca or kola, especially Dr Tibbles’ Vi-Cocoa, and milk powders (Plasmon and Sanatogen). All of these were legitimised using new scientific knowledge, but the claims that underpinned them did not emerge only from the orthodox science of nutrition; scientific and medical practitioners also used other kinds of scientific knowledge to justify products containing compounds that most nutrition practitioners believed did not require supplementation or that they considered were not foods at all. However, knowledge was deployed selectively; interdisciplinary inconsistencies do not appear to have mattered, and although scientific legitimacy seems to have been necessary, Health Foods’ popularity also rested on their social and cultural framing which ostensibly was unrelated to their scientific properties. This framing was achieved through the collective efforts of manufacturers, politicians, scientists, commentators, and consumers. Accordingly, eating Health Foods became positioned as respectable and frugal, and came to signify pleasure and know-how. These banal products came to offer a sense of community and national identity, alongside enhanced physical or nervous energy, strength, and stamina. They purportedly enabled women to fulfil their duty of care, and men to be productive workers, because they responded to widespread anxieties about modernity and decline. However, they were not equivalents or universal panaceas for all. Each one became understood as enabling particular kinds of people to enact particular roles and behaviours that eaters considered desirable in specific social and gender contexts, and so also afford us insights into the various ways of being that were desirable at the fin de siècle.