Dietary Screener Questionnaire in the NHIS CCS 2010: Data Processing and Scoring Procedures
Our NCI research team followed several steps to formulate the Dietary Screener Questionnaire (DSQ) scoring algorithms. These steps are described for researchers who may be interested in the methodologic process our team used. However, it is not necessary for researchers to follow these steps; a SAS program [SAS - 18 KB] that integrates these steps is publicly available, as are computed variables for the dietary variables in the NHIS CCS.
Our steps consisted of:
- converting frequency data to daily frequency,
- identifying extreme exposure values, and
- classifying cereal data.
Developing scoring algorithms
We developed scoring algorithms to convert screener responses to estimates of individual dietary intake for fruits and vegetables (cup equivalents), dairy (cup equivalents), added sugars (tsp), added sugars from sugar-sweetened beverages, whole grains (ounce equivalents), fiber (g), and calcium (mg) using the What We Eat in America 24-hour dietary recall data from the 2003-2006 NHANES. Equations were estimated in the NHANES 2003-2006, using SAS PROC REG.
Using the equations (see above), we performed the following steps to estimate the individual intake of fruits and vegetables (cup equivalents), dairy (cup equivalents), added sugars (tsp), whole grains (ounce equivalents), fiber (g), and calcium (mg).
Estimation of Pk:
The median sex- and age-specific portion sizes for each food were estimated from NHANES 2003-2006. For fruit and vegetable variables, the unit was MyPyramid* cup equivalents (Table 1). For dairy, the unit was MyPyramid cup equivalents (Table 2). For added sugars and sugar-sweetened beverages the unit was MyPyramid teaspoons of added sugars (Table 3 and Table 4). For whole grains, the unit was grams (Table 5). For fiber and calcium, the unit was grams (Table 6).
For fruits and vegetables, a MyPyramid cup equivalent is defined by the U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (HHS) in the Dietary Guidelines for Americans, 2010 as:
- vegetables: 1 cup raw or cooked; 1 cup vegetable juice; or 2 cups leafy salad greens
- fruit: 1 cup raw or cooked; ½ cup dried fruits; or 1 cup fruit juice.
For dairy, a MyPyramid cup equivalent is defined by the USDA and HHS in the Dietary Guidelines for Americans, 2010 as:
- 1 cup milk, fortified soy beverage, or yogurt
- 1 ½ ounces of natural cheese
- 2 ounces of processed cheese
The exposure sugar-sweetened beverages is defined in the Dietary Guidelines for Americans, 2010 as: "Liquids that are sweetened with various forms of sugars that add calories. These beverages include, but are not limited to, soda, fruitades and fruit drinks, and sports and energy drinks." For our analyses, we defined this exposure as including the above types of drinks plus coffees and teas when sweetened with sugar.
For whole grains, a MyPyramid ounce equivalent is defined by the USDA and HHS in the Dietary Guidelines for Americans, 2010 as:
- 1 one-ounce slice of whole grain bread
- 1 ounce of uncooked whole grain pasta or rice
- ½ cup of cooked whole grain rice, pasta, or cereal
- 1 whole grain tortilla (6 inch diameter)
- 1 whole grain pancake (5 inch diameter)
- 1 ounce (or about 1 cup cereal flakes) ready-to-eat whole grain cereal.
* MyPyramid is a food guidance system featured in the Dietary Guidelines for Americans, 2005. In order to examine food intakes in relation to MyPyramid, the MyPyramid Equivalent Database (MPED) was developed. It translates reported food intake into guidance-based food groups. The 2010 Dietary Guidelines used an update to USDA's food pattern guidance, and more recent versions of the MPED are now called Food Pattern Equivalent Databases (FPED). The FPEDs for 2009-10 24-hour recall data are not yet released. The algorithms described here will be updated when they are released.