Despite more than a century of detailed investigation of the Magdalenian period in Northern Iberia, our understanding of the diets during this period is limited. Methodologies for the reconstruction of Late Glacial subsistence strategies have overwhelmingly targeted animal exploitation, thus revealing only a portion of the dietary spectrum. Retrieving food debris from calculus offers a means to provide missing information on other components of diet.We undertook analysis of human dental calculus samples from Magdalenian individuals (including the ¿Red Lady¿) at El Mir on Cave (Cantabria, Spain), as well as several control samples, to better understand the less visible dietary components. Dental calculus yielded a diverse assemblage of microremains from plant, fungal, animal and mineral sources that may provide data on diet and environment. The types of microremains show that the individuals at El Mir on consumed a variety of plants, including seeds and underground storage organs, as well as other foods, including possibly bolete mushrooms. These findings suggest that plant and plant-like foods were parts of her diet, supplementing staples derived from animal foods. As faunal evidence suggests that the Magdalenian Cantabrian diet included a large proportion of animal foods, we argue here for a mixed subsistence pattern.