Using 2008 household data and a two-step censored model, this article analyzes separability among preferences of the major food groups in Mexico. The main objective of the present paper was to determine if beans and potatoes are not separable from meats and cereals, respectively. Results indicate that beans belong to the protein source demand system and potatoes are not separable from cereals. Another major finding is that corn income elasticity very close to one might indicate a sensitive situation for low income households that consider this cereal their major source of calories.