Classifying Cereal Data
The DSQ includes questions about cereal intake and allows respondents to choose up to two responses from a listing of cereals as to which they consumed most frequently. A total of 391 cereal names, including generic or not further specified ones, are on the listing, and 283 are distinct entities.
We classified each of the 283 distinct cereals listed along four dimensions: density of added sugars, whole grains, fiber, and calcium. In the scoring algorithms, all categories have different regression coefficients that relate them to the various dietary factors.
Processing of the cereal data consisted of:
- Identification of distinct cereals. Determine cereal categories based on nutrient density. For each nutrient, i.e. added sugars, whole grains, fiber, and calcium, we ordered listed cereals by density (nutrient/100 grams). We then divided each distribution into tertiles. Note: this density categorization was based on the cereal composition and not the absolute frequency of reported consumption.
- Application of this classification to all listed cereals. Thus each cereal listed is coded along the following attributes: category for added sugars; category for whole grains; category for fiber; and category for calcium.
- Weighting each cereal frequency according to order of report. For those respondents who reported two different cereal types, we assumed that the first cereal reported was the most frequently consumed and the second was less frequently consumed. Accordingly, we weighted the first cereal at 0.75 and the second at 0.25. For those who reported only one cereal type, no weighting was necessary.
Following are the classification criteria for cereals by nutrient density. Note that any given cereal may fall into different tertiles for different nutrients.
Table 1: Classification Criteria for Hot and Cold Cereals with Regard to Added Sugars Density
|Cereal||Density (tsp added sugars/100 grams)||No. of cereals|
|Lowest tertile added sugars||≤0.71||94|
|Second tertile added sugars||0.72 - 5.49||95|
|Highest tertile added sugars||>5.49||94|
Table 2: Classification Criteria for Cereals with Regard to Whole Grain Density
|Cereal||Density (ounce-equivalents of whole grains/100 grams)||No. of cereals|
|Lowest tertile whole grain||≤0.21||94|
|Second tertile whole grain||0.22 - 1.40||94|
|Highest tertile whole grain||>1.40||95|
Table 3: Classification Criteria for Cereals with Regard to Fiber Density
|Cereal||Density (grams of fiber/100 grams)||No. of cereals|
|Lowest tertile fiber||≤2.1||92|
|Second tertile fiber||2.2 - 7.3||96|
|Highest tertile fiber||>7.3||95|
Table 4: Classification Criteria for Hot and Cold Cereals with Regard to Calcium Density
|Cereal||Density (milligrams of calcium/100 grams)||No. of cereals|
|Lowest tertile calcium||≤21||95|
|Second tertile calcium||22-100||94|
|Highest tertile calcium||>100||94|
Cereal data can be reported in different formats. The format used in the NHANES DSQ was 8-digit FNDDS food codes. Table 5 (XLS | CSV) shows the food codes and attributes for the cereals reported in this format.
Cereal data reported on the self-administered web version is in a character (i.e. letters) format. Table 6 shows the food codes and attributes for the cereal choices in the self-administered web version of the questionnaire.