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Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
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Appendix K

Diet Quality Indexes

As described in the 2015 Institute of Medicine (IOM) report Review of WIC Food Packages: An Evaluation of White Potatoes in the Cash Value Voucher: Letter Report, options for a second index were considered by the committee based on its evaluation of the literature on existing diet quality indexes other than the Healthy Eating Index-2010 (HEI-2010) and with consideration to three criteria: (1) the index can be applied to adults and children, (2) 24-hour recall data are applied, and (3) the index is based on a metric other than comparison to the Dietary Guidelines for Americans (DGA). After reviewing potential indexes, the committee determined that responding to the task would require an index that focuses mainly on nutrient content to provide a contrast to the food-group focus of the HEI-2010. However, the committee found that existing nutrient-based indexes could not be applied directly for two reasons. First, they could not be applied because they use Daily Values based on a 2,000-calorie diet as reference standards for nutrient intake rather than age-appropriate Dietary Reference Intake (DRI) values. Second, they do not necessarily include all of the nutrients and dietary components the committee was interested in assessing, based on current knowledge about nutrients of concern in the diets of young children and women of childbearing age (the 2010 DGA) and the committee’s assessment of the nutrient intakes of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC)-eligible populations. The committee developed an adapted nutrient-based diet quality index to be scored by comparison to DRI values. The components of this index are described here.

The index examined the following “positive” nutrients included in the

Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
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2015 Dietary Guidelines Advisory Council (DGAC) as shortfall nutrients and nutrients of concern, to be updated upon release of the 2015 DGA:

  1. Potassium
  2. Dietary fiber
  3. Calcium
  4. Iron
  5. Vitamin C
  6. Folate
  7. Vitamin A
  8. Vitamin E
  9. Magnesium

The index is the mean percentage adequacy for these nine nutrients, calculated for each individual. The possible range is from 0 to 100.

  • For nutrients with an Estimated Average Requirement (EAR): the percentage adequacy was calculated for each individual for each day. To do this, the method described in IOM (2000) was applied using the DRI for assessment of intake of individuals and groups and z-scores were computed for each respondent as follows:
    1. Usual intake at the individual level was first estimated as the best linear unbiased predictor of intake (BLUP). The BLUP has the smallest prediction error variance among all linear predictors.
    2. The difference between the individual’s estimated usual intake of the nutrient and the EAR for the nutrient was then computed.
    3. A z-score was computed as the ratio of the difference to the standard error of that difference.
    4. Finally, the probability of observing a z-value that was at least as large as the one observed for the individual was computed and multiplied by 100. These calculations were repeated for all the nutrients included in the index. The possible range is from 0 to 100.
  • For the nutrients with an Adequate Intake (AI) value (potassium and dietary fiber), reasonable intake ranges based on the AI were applied, to assign 0, 25, 50, and 100 percent adequacy as follows:
    1. Intake equal to or above the AI, percentage adequacy = 100.
    2. Intake below the AI but equal to or above 75 percent of the AI, percentage adequacy = 75.
    3. Intake below 75 percent of the AI but equal to or above 50 percent of the AI, percentage adequacy = 50.
Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
×
    1. Intake below 50 percent of the AI but equal to or above 25 percent of the AI, percentage adequacy = 25.
    2. Intake below 25 percent of the AI, percentage adequacy = 0.
  • The mean percentage adequacy for each individual was calculated by averaging the nutrient-wise percentage adequacy.
  • The mean percentage adequacy for population subgroups was then calculated using individual survey weights. Initial descriptive statistics generated to validate the index:
    1. As a first step, the mean and standard deviation of the index was evaluated.
    2. Second, the association of the index with energy intake was examined.
    3. Finally, the association with the HEI-2010 was examined.
  • Image
    FIGURE K-1 Nutrient adequacy index distributions of WIC children ages 1 to less than 2 years, 2005–2008.
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Image
    FIGURE K-2 Nutrient adequacy index distributions of WIC children ages 2 to less than 5 years, 2005–2008.
    Image
    FIGURE K-3 Nutrient adequacy index distributions of WIC women ages 19 to less than 50 years.
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×

    TABLE K-1 HEI-2010 Components and Scoring System

    HEI-2010 Componenta Maximum Standard for Maximum Score Standard for Minimum Score of Zero
    Adequacy
    Total Fruitb 5 ≥ 0.8 c-eq / 1,000 kcal No fruit
    Whole Fruitc 5 ≥ 0.4 c-eq / 1,000 kcal No whole fruit
    Total Vegetablesd 5 ≥ 1.1 c-eq / 1,000 kcal No vegetables
    Greens and Beansd 5 ≥ 0.2 c-eq / 1,000 kcal No dark green vegetables, beans, or peas
    Whole Grains 10 ≥ 1.5 c-eq / 1,000 kcal No whole grains
    Dairye 10 ≥ 1.3 c-eq / 1,000 kcal No dairy
    Total Protein Foodsf 5 ≥ 2.5 c-eq / 1,000 kcal No protein foods
    Seafood and Plant Proteinsf,g 5 ≥ 0.8 c-eq / 1,000 kcal No seafood or plant proteins
    Fatty Acidsh 10 (PUFAs + MUFAs) / SFAs ≥ 2.5 (PUFAs + MUFAs) / SFAs ≤ 1.2
    Moderation
    Refined Grains 10 ≥ 1.8 oz-eq / 1,000 kcal ≥ 4.3 oz-eq / 1,000 kcal
    Sodium 10 ≥ 1.1 g / 1,000 kcal ≥ 2.0 g / 1,000 kcal
    Empty Caloriesi 20 ≥ 19 percent of energy ≥ 50 percent of energy

    NOTES: c-eq = cup-equivalent; HEI = Healthy Eating Index; kcal = kilocalorie; oz-eq = ounce-equivalent; MUFA = monounsaturated fatty acid; PUFA = polyunsaturated fatty acid; SFA = saturated fatty acid.

    a Intakes between the minimum and maximum standards are scored proportionately.

    b Includes 100% fruit juice.

    c Includes all forms except juice.

    d Includes any beans and peas not counted as Total Protein Foods.

    e Includes all milk products such as fluid milk, yogurt, and cheese, and fortified soy beverages.

    f Beans and peas are included here (not with vegetables) when the Total Protein Foods standard is otherwise not met.

    g Includes seafood, nuts, seeds, soy products (other than beverages) as well as beans and peas counted as Total Protein Foods.

    h Ratio of poly- and monounsaturated fatty acids (PUFAs and MUFAs) to saturated fatty acids (SFAs).

    I Calories from solid fats, alcohol, and added sugars; threshold for counting alcohol is > 13 grams / 1,000 kcal.

    SOURCE: Guenther et al., 2013.

    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×

    REFERENCES

    Guenther, P. M., K. O. Casavale, J. Reedy, S. I. Kirkpatrick, H. A. Hiza, K. J. Kuczynski, L. L. Kahle, and S. M. Krebs-Smith. 2013. Update of the Healthy Eating Index: HEI-2010. Journal of the Academy of Nutrition and Dietetics 113(4):569-580.

    IOM (Institute of Medicine). 2000. Dietary reference intakes: Applications in dietary assessment. Washington, DC: National Academy Press.

    IOM. 2015. Review of WIC food packages: An evaluation of white potatoes in the cash value voucher: Letter report. Washington, DC: The National Academies Press.

    USDA/HHS (U.S. Department of Agriculture/U.S. Department of Health and Human Services). 2015. The report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 2015, to the Secretary of Agriculture and the Secretary of Health and Human Services. Washington, DC: USDA/HHS. http://www.health.gov/dietaryguidelines/2015-scientific-report/PDFs/Scientific-Report-of-the-2015-DietaryGuidelines-Advisory-Committee.pdf (accessed May 24, 2015).

    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Page 431
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Page 432
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Page 433
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Page 434
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Page 435
    Suggested Citation:"Appendix K: Diet Quality Indexes." National Academies of Sciences, Engineering, and Medicine. 2016. Review of WIC Food Packages: Proposed Framework for Revisions: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/21832.
    ×
    Page 436
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    The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) began 40 years ago as a pilot program and has since grown to serve over 8 million pregnant women, and mothers of and their infants and young children. Today the program serves more than a quarter of the pregnant women and half of the infants in the United States, at an annual cost of about $6.2 billion. Through its contribution to the nutritional needs of pregnant, breastfeeding, and post-partum women; infants; and children under 5 years of age; this federally supported nutrition assistance program is integral to meeting national nutrition policy goals for a significant portion of the U.S. population.

    To assure the continued success of the WIC, Congress mandated that the Food and Nutrition Service of the U.S. Department of Agriculture (USDA) reevaluate the program's food packages every 10 years. In 2014, the USDA asked the Institute of Medicine to undertake this reevaluation to ensure continued alignment with the goals of the Dietary Guidelines for Americans. This, the second report of this series, provides a summary of the work of phase I of the study, and serves as the analytical underpinning for phase II in which the committee will report its final conclusions and recommendations.

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