Distinguishing between food, food substitutes and supplements is common in everyday life and academic work. The aim of this paper is to analyze this distinction. The question is approached from the point of view of functions. The hypothesis reads as follows: “Food has several nutritional, culinary, social, cultural, aesthetic and other functions. These functions are necessary and sufficient for something to be food. Food substitutes and supplements, serve some, but not many, functions of food. Thus, food substitutes and supplements are not food”. The contemplations of the paper speak against accepting the hypothesis. This negative view is reached by defining the central terms, discussing the differences between eating and swallowing, analyzing the different meanings of the term ‘edible’ and a throughout analysis of functions of food, substitutes and supplements. As a part of the discussion an idea of origin based functions is developed. If the hypothesis is false (as argued), then the distinction between food and other edible entities must be based on something else than differences in functions. Alternatively the distinction may lack metaphysical justification. The view following this latter alternative is developed for the purpose of further studies.