This study analyzes U.S. consumers' demand for eight food commodity groups: Cereal and Bakery goods, Meat and Eggs, Dairy, Fruits and Vegetables, Nonalcoholic Beverages, Fats and Oils, Sugar and Sweets, and Miscellaneous goods. The data used in this study is Nielsen Homescan data for the period 2002-2006. Three different levels of temporal aggregation, biweekly, monthly and yearly were considered. We conclude that the data collection period does affect the value of elasticities obtained from estimated food demand models. Moreover, larger biases in the estimated elasticities are likely to be present even when using econometric methods currently recommended to account for this problem.