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Dietary Screener in the 2009 CHIS: Scoring Procedures

How Analytical Scoring Procedures Were Developed

Scoring procedures were developed to convert the individual respondent's screener responses to estimates of intake. We created variables for amount consumed of each food group queried, and for amount consumed of total fruits and vegetables (cup equivalents) and added sugars (teaspoons). To do so, we used 24-hour dietary recall data from the National Center for Health Statistics (NCHS) National Health and Nutrition Examination Survey (NHANES) 2003-2006.

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Conversion of frequency category to times per day

Data collected on the 2009 California Health Interview Survey (CHIS) Dietary Screener consist of frequency response and time unit: times per day, week, or month. We converted these responses to daily frequency values, denoted as NFGk and shown below.

Time Period Reported NFGk: Daily Frequency
Day As reported
Week Reported frequency divided by 7
Month Reported frequency divided by 30

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Exclusion of extreme values

We examined each variable’s distribution of values for times per day. For each dietary variable, values discontinuous with the overall CHIS distribution were excluded. The maximum daily acceptable value and the number of cases excluded are shown below.

Food Group Maximum Daily Acceptable Value Number of Cases Excluded
Fruit 10 2
Fried potatoes 5 0
Other vegetables 10 0
Regular soda 8 7
Sports/energy drinks + Fruit drinks 11 1
Sugar in coffee and tea 12 5
Cookies, cake, pie, brownies 10 0
Ice cream 6 1

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Estimation of median sex-age portion sizes

We estimated the median sex- and age-specific portion sizes for each food from 24-hour recall data in NHANES 2003-2006. The units used were specific to each food group: cup equivalents of fruits and vegetables for fruit, fried potatoes, and other vegetables, and teaspoons of added sugars for soda, energy/fruit drinks, coffee/tea, cookies/cake/pie/brownies, and ice cream. These portion sizes are denoted by Pk.

For fruits and vegetables, cup equivalents are defined in the US Department of Agriculture’s (USDA) MyPyramid Equivalents Database (MPED; version 2.0 for USDA Survey Foods, 2003-2004) and cited in the US Dietary Guidelines for Americans 2010 as:

  • 1 cup raw or cooked vegetable or fruit
  • 1/2 cup dried vegetable or fruit
  • 1 cup vegetable or fruit juice
  • 2 cups leafy salad greens.

Median portion sizes for fruits and vegetables are given as cup equivalents of fruits and vegetables:

Median Portion Size (Pk) in Cup Equivalents per Mention by Sex and Age for Fruits and Vegetables Analyses
Food Group Age Group
18-27 28-37 38-47 48-57 58-67 68-77 78-99
Men
Fruit (P1) 0.867300 0.911790 0.867300 0.867300 0.813000 0.715500 0.713000
Fried potatoes (P2) 0.622000 0.663435 0.548000 0.548055 0.545000 0.455000 0.444000
Other vegetables (P3) 0.424210 0.475600 0.511000 0.537500 0.535714 0.515400 0.468600
Women
Fruit (P1) 0.764240 0.750000 0.739187 0.775915 0.742000 0.633000 0.632000
Fried potatoes (P2) 0.480000 0.446660 0.444000 0.385000 0.455275 0.444000 0.320000
Other vegetables (P3) 0.392600 0.440000 0.470974 0.481716 0.473689 0.447818 0.434007

For added sugars, median portion sizes are given as teaspoons of added sugars:

Median Portion Size (Pk) in Teaspoons per Mention by Sex and Age for Added Sugars Analyses
Food Group Age Group
18-27 28-37 38-47 48-57 58-67 68-77 78+
Men
Regular soda (P1) 11.601377 10.480288 10.327300 9.428160 8.994700 8.994700 7.889000
Fruit drinks + sports drinks (P2) 8.559500 8.232800 10.264077 8.141300 7.558200 5.439624 5.439624
Cookies, cake, pie (P3) 3.761000 3.756900 4.387860 3.735000 3.192000 3.230824 2.667387
Ice cream (P4) 5.052000 5.262000 5.052000 4.680000 4.508965 3.691000 3.849000
Sugars in coffee/tea (P5) 2.000124 2.000124 2.500155 2.484333 1.500000 1.488188 1.653277
Women
Regular soda (P1) 9.336096 8.947000 7.953000 8.617500 7.865340 7.295500 5.917000
Fruit drinks + sports drinks (P2) 7.258570 7.493000 6.451665 6.230040 6.798000 4.536750 4.113113
Cookies, cake, pie (P3) 2.661000 3.340980 3.651000 3.208920 2.821134 2.729500 2.572640
Ice cream (P4) 3.509870 3.875520 3.300180 3.094000 2.949000 3.350500 3.300180
Sugars in coffee/tea (P5) 2.000000 2.000124 2.000000 1.666770 1.500000 1.382000 1.000062

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Creation of food-level variables

Food-level variables were created for each food queried by multiplying the individual's standardized daily frequency of intake by his/her sex-age specific portion size, denoted by:

Estimated amount consumed daily of Food Groupk = NFGkP1

The following food-level variables are available:

Variable Name Label
FRUIT Unadjusted daily cup equivalents of fruits
FRIED_PO Unadjusted daily cup equivalents of fried potatoes
VEG_OTH Unadjusted daily cup equivalents of other vegetables
SUG_SODA Unadjusted daily teaspoons of added sugar in soda
SUG_ENGD Unadjusted daily teaspoons of added sugar in fruit/energy drinks
SUG_COFF Unadjusted daily teaspoons of added sugar in coffee and tea
SUG_BEV Unadjusted daily teaspoons of added sugar in all beverages
SUG_PAST Unadjusted daily teaspoons of added sugar in pastries
SUG_ICRM Unadjusted daily teaspoons of added sugar in ice cream

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Creation of aggregate variables

A. Fruit and Vegetable Intake

For estimates of fruits and vegetables aggregated across all food questions:

E(Fruits and Veg1/2) = b0 + b1(NFG1P1 + NFG2P2 + NFG3P3)1/2

The cup equivalents of fruits and vegetables variable was square-root-transformed to approximate normality; NFGk is the usual number of times per day an individual consumed food group k; k indexes the three fruit and vegetable food groups. Pk is the median portion size of group k. We calculated weighted least-squares estimates of the regression coefficients b0 and b1 on the adults (aged 18 and above) in the NHANES 2003-2006 sample, stratifying by sex and excluding extreme exposure values.

Estimation of b0 and b1: For cup equivalents of fruits and vegetables excluding dried beans and French fries, the sex-specific estimates of the parameters are:

Estimated Regression Coefficients for Sum of Foods Predicting Different Versions of Daily Cup Equivalents of Fruits and Vegetables, by Sex
Parameter Men Women
Summary Variable with French fries, excluding beans
Intercept (b0) 0.900416 0.763098
b1 0.648026 0.673026
Summary Variable excluding French fries and beans
Intercept (b0) 0.907261 0.641925
b1 0.774934 0.662708

B. Added Sugars Intake

For teaspoons of added sugars:

E(Added sugars1/3) = b0 + b1 (NFG1P1 + NFG2P2 + ... + NFG5P5)1/3

The teaspoons of added sugars variable was cube-root-transformed to approximate normality; NFGk is the usual number of times per day an individual consumed food group k; k indexes the five added sugars food groups. Pk is the median portion size of group k. We calculated weighted least-squares estimates of the regression coefficients b0 and b1 on the adults (aged 18 and above) in the NHANES 2003-2006 sample, stratifying by sex and excluding extreme exposure values.

Estimation of b0 and b1: For teaspoons of added sugars, the sex-specific estimates of the parameters are:

Estimated Regression Coefficients for Sum of Foods Predicting Teaspoons of Added Sugars, by Sex
Parameter Men Women
Intercept (b0) 1.434353 1.436804
b1 0.605576 0.547127

The following aggregated variables were created:

Variable Name Label
FV_NOBNS Daily cup equivalents of fruits & vegetables excluding beans
FV_NOFBN Daily cup equivalents of fruits/veg excl french fries & beans
SUGAR2 Daily teaspoons of added sugar

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Variance adjustment factors

In addition to these variables, we applied variance adjustment factors to create variance-adjusted versions of each for use in many analytical situations.

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Last Modified: 11 Apr 2014