Development and validation of a food-based diet quality index for New Zealand adolescents

Jyh Eiin Wong, Winsome R. Parnell, Anna S. Howe, Katherine E. Black, Paula M L Skidmore

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Background: As there is no population-specific, simple food-based diet index suitable for examination of diet quality in New Zealand (NZ) adolescents, there is a need to develop such a tool. Therefore, this study aimed to develop an adolescent-specific diet quality index based on dietary information sourced from a Food Questionnaire (FQ) and examine its validity relative to a four-day estimated food record (4DFR) obtained from a group of adolescents aged 14 to 18 years. Methods. A diet quality index for NZ adolescents (NZDQI-A) was developed based on 'Adequacy' and 'Variety' of five food groups reflecting the New Zealand Food and Nutrition Guidelines for Healthy Adolescents. The NZDQI-A was scored from zero to 100, with a higher score reflecting a better diet quality. Forty-one adolescents (16 males, 25 females, aged 14-18 years) each completed the FQ and a 4DFR. The test-retest reliability of the FQ-derived NZDQI-A scores over a two-week period and the relative validity of the scores compared to the 4DFR were estimated using Pearson's correlations. Construct validity was examined by comparing NZDQI-A scores against nutrient intakes obtained from the 4DFR. Results: The NZDQI-A derived from the FQ showed good reliability (r = 0.65) and reasonable agreement with 4DFR in ranking participants by scores (r = 0.39). More than half of the participants were classified into the same thirds of scores while 10% were misclassified into the opposite thirds by the two methods. Higher NZDQI-A scores were also associated with lower total fat and saturated fat intakes and higher iron intakes. Conclusions: Higher NZDQI-A scores were associated with more desirable fat and iron intakes. The scores derived from either FQ or 4DFR were comparable and reproducible when repeated within two weeks. The NZDQI-A is relatively valid and reliable in ranking diet quality in adolescents at a group level even in a small sample size. Further studies are required to test the predictive validity of this food-based diet index in larger samples.

Original languageEnglish
Article number562
JournalBMC Public Health
Volume13
Issue number1
DOIs
Publication statusPublished - 2013

Fingerprint

New Zealand
Diet
Food
Fats
Iron
Nutrition Policy
Reproducibility of Results
Sample Size
Surveys and Questionnaires

Keywords

  • Adolescents
  • Diet quality index
  • Dietary patterns
  • New Zealand
  • Validity

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

Cite this

Development and validation of a food-based diet quality index for New Zealand adolescents. / Wong, Jyh Eiin; Parnell, Winsome R.; Howe, Anna S.; Black, Katherine E.; Skidmore, Paula M L.

In: BMC Public Health, Vol. 13, No. 1, 562, 2013.

Research output: Contribution to journalArticle

Wong, Jyh Eiin ; Parnell, Winsome R. ; Howe, Anna S. ; Black, Katherine E. ; Skidmore, Paula M L. / Development and validation of a food-based diet quality index for New Zealand adolescents. In: BMC Public Health. 2013 ; Vol. 13, No. 1.
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AB - Background: As there is no population-specific, simple food-based diet index suitable for examination of diet quality in New Zealand (NZ) adolescents, there is a need to develop such a tool. Therefore, this study aimed to develop an adolescent-specific diet quality index based on dietary information sourced from a Food Questionnaire (FQ) and examine its validity relative to a four-day estimated food record (4DFR) obtained from a group of adolescents aged 14 to 18 years. Methods. A diet quality index for NZ adolescents (NZDQI-A) was developed based on 'Adequacy' and 'Variety' of five food groups reflecting the New Zealand Food and Nutrition Guidelines for Healthy Adolescents. The NZDQI-A was scored from zero to 100, with a higher score reflecting a better diet quality. Forty-one adolescents (16 males, 25 females, aged 14-18 years) each completed the FQ and a 4DFR. The test-retest reliability of the FQ-derived NZDQI-A scores over a two-week period and the relative validity of the scores compared to the 4DFR were estimated using Pearson's correlations. Construct validity was examined by comparing NZDQI-A scores against nutrient intakes obtained from the 4DFR. Results: The NZDQI-A derived from the FQ showed good reliability (r = 0.65) and reasonable agreement with 4DFR in ranking participants by scores (r = 0.39). More than half of the participants were classified into the same thirds of scores while 10% were misclassified into the opposite thirds by the two methods. Higher NZDQI-A scores were also associated with lower total fat and saturated fat intakes and higher iron intakes. Conclusions: Higher NZDQI-A scores were associated with more desirable fat and iron intakes. The scores derived from either FQ or 4DFR were comparable and reproducible when repeated within two weeks. The NZDQI-A is relatively valid and reliable in ranking diet quality in adolescents at a group level even in a small sample size. Further studies are required to test the predictive validity of this food-based diet index in larger samples.

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