Prior to 2000, respondents were asked about foods they usually ate in the past year. Beginning in 2000, this recall period was reduced to foods the respondent usually ate in the past month. The structure of the responses beginning in 2000 excluding 2005 (recording number of times a food was consumed and the time unit associated with that frequency) makes it possible to compare response categories even with different recall periods. In 2005, this format of separate frequency and time units was not used; instead respondents' answers were organized into pre-defined categories. Researchers interested in using more years of available data may consider seeing the 2005 variable CEREALMO, and modifying CEREALMNO and CEREALMTP (or CEREALYR) to correspond to the pre-defined categories from 2005.

Prior to 2000, respondents were asked about hot or cooked cereals (e.g., oatmeal), high fiber cereals (e.g., granola), highly fortified cereals (e.g., Total, Product 19, or Just Right), and other cold cereals separately. In 2000, respondents were only asked to report their consumption of cold cereal. In 2005, response categories for types of cereal include hot or cooked cereals, all bran cereals, cereals with some bran or fiber, cereals with little bran or fiber, and other cold cereals. Beginning in 2010, respondents listed the specific type of cereal verbatim, rather than a general type of cereal.

Data users wishing to compare cereal consumption across multiple years might consider CEREALYR, a recoded variable the reports total cereal consumption per year. CEREALTYPE reports the type of cereal the respondent reported consuming most. Prior to 2010, respondents were asked about pre-defined categories of cereal (e.g., all bran cereals, low-bran or fiber cereals, cooked cereals, etc.). Beginning in 2010, types of cereal were recorded as verbatim responses, including specific cereal types and brands. Given the single cereal type in 2000 and the large number of more specific cereal types beginning in, these samples are not included in CEREALTYPE.