Objective: To describe and compare the everyday knowledge about plain water consumption among "small" and "big drinkers".
Materials and methods: A qualitative study was conducted between April and August 2010 in Mexico. Eight focus groups with low socioeconomic status adults as key informants were conformed; half of the groups were conducted with men and half with women. Data analysis was conducted with: a) coding and categorization according to hydration literature review b) conceptual mapping, recognizing propositions and affirmations made by the participants.
Results: Small and big drinkers have similar everyday knowledge about plain water intake. Both groups use the same epistemological axes to explain its intake: "what the body needs". Both groups have the notion that plain water and other beverages such as soda "may be harmful" if you drink them in excess.
Conclusions: Everyday knowledge about water is related to soda and drinks used to substitute water intake. The characteristics of water and soda intake are constructed based on personal experience and insights on their effect on the body and mind. These representations can be used to assess fluid intake and may constitute barriers to the consumption of plain water.