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Validation of dietary assessment methods 1990 - present

Heather Ward, Natasha Powell, Sheila Bingham, and Kay Tee Khaw, University of Cambridge

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Search criteria

Inclusion criteria• English language articles, 1990 - June 2008, within the European Union • Relative validity assessed • Free-living, non-pregnant population

Exclusion criteria• Dietary instrument specific to certain nutrients or foods • Feeding study or intervention

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Search engine and key words

Search engine ISI Web of Knowledge

Keywords diet/food/nutrition + energy intake or EI, basal metabolic rate or BMR, calibration, biomarker, carotenoid, validation, urin* nitrogen, urin* potassium, fatty acid, doubly labeled water, plasma vitamin C, urinary thiamine

10,661

met regional criteria

= 98

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reference lists

82

met inclusion/exclusion

criteria

+

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Biomarkers used in majority of studies

66% validated against biomarkers

34% compared to other reported dietary instruments

Method n

Diet diary (DD) 28

Diet history (DH) 12

Food frequency questionnaires (FFQ)

66

24hour recall (24HR) 24

Weighed food record (WFR)

33

Other 9

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Biomarkers used in majority of studies

• 61 self-administered

• Avg. 134 items (min 27, max 254)

• Portion estimates:standard/natural units (n = 31), photos (n = 16),or both (n = 10)

Method n

Diet diary (DD) 28

Diet history (DH) 12

Food frequency questionnaires (FFQ)

66

24hour recall (24HR) 24

Weighed food record (WFR)

33

Other 9

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Biomarker Categories

1) Recovery: Doubly labeled water, 24hour urinary nitrogen, 24hr urinary potassium

2) Concentration: Plasma βcar, serum ascorbic acid, serum tocopherol, serum retinol, serum/adipose tissue fatty acids

3) Replacement: 24hr urinary sodium, serum/urinary phytoestrogens

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Diverse associations between FFQ and recovery biomarkers

1) Doubly labeled water > FFQ-energy by 22%, r 0.48 20

2) 24hr urinary nitrogen vs. FFQ-protein:• ‘Incomplete’ urine r 0.18 38 – 0.67 33 • Complete urine r 0.15 27, 31– 0.46 20

• r NS 0.27 upon exclusion of incomplete urine 36

3) 24hr urinary potassium vs. FFQ-potassium:• Incomplete r NS 34, 35

• Complete r < 0.35 24, 25, 27, 28, 31

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Concentration biomarkers: indicators of intake

1) Plasma βcar vs. FFQ-βcar:• r NS 35,41,47 or < 0.28 15, 24, 40, 44, 48

• 9d FFQs r 0.32 (women), r 0.47 (men) 49

2) Serum ascorbic acid vs. FFQ-vitamin C• r NS 35

or r 0.30 – 0.56 15,25, 28, 49, 56, 58, 59

Smoking decreases serum ascorbic acid levels• Smokers r 0.46, non-smokers r 0.56 58

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Concentration biomarkers (continued)

3) Serum retinol NS r with FFQ-vitamin A 41, 58, 63

4) Serum/plasma tocopherol NS r with

FFQ-vitamin E 35, 44, 58, 63, 64

5) Fatty acids (FA)• Serum FA vs. FFQ-FA r 0.26 – 0.56 64,67,68

• Adipose tissue FA vs. FFQ-FA r 0.15 – 0.79 64, 67, 69 -72

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Replacement biomarkers: indicators for difficult-to-quantify nutrients

1) 24hr urinary sodium vs. FFQ-sodium• Incomplete, r NS 34,41

• Complete, r 0.20 28

2) Serum/urinary phytoestrogens vs. FFQ-phytoestrogens and soy-based foods

• r 0.24 – 0.27, men 76

• r 0.28 – 0.74, women 77

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Summary of FFQs vs. biomarkers

• Moderate r values (0.5 or below), many NS

• Objective indicators

• Independent sources of error relative to self-reported instruments

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FFQ vs. WFR (19 studies)

• FFQ > WFR in some studies 7,24,37,81,82, but not all34,54,64,83-86

• r range 0.21 – 0.78

• Highest r generally for alcohol 7,25,34,37,88,90

• 30 – 82% classified into same/adjacent quantile by both methods, < 20% extremely misclassified 25, 37, 64, 82 – 84, 86,87,90

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FFQ vs. DD (12 studies)

• FFQ > DD when means tested 27,28,31,33,36,47,62,74,91-94

• r range 0.14 – 0.79

• Highest r for alcohol, with one exception 92

• 32 – 89% classified into same/adjacent quantile by both methods, < 36% extremely misclassified 28,47,74, 91,92

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FFQ vs. 24HR (14 studies)

• FFQ > 24HR in many studies 40,41,48,73,96,98-100, but not all 20, 38,43,101,102

• r 0.14 – 0.77 (higher for alcohol); generally improved with more 24HR, energy adjustment and de-attenuation

• 23 – 87% classified into same/adjacent quantile by both methods, < 10% extremely misclassified 20,40,43,96-99

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Limitations of FFQ comparisons

• Temporal sequence: reference then test instrument

• Cross-quantile results difficult to interpret when used for all nutrients under study

• Broad examination may have missed nutrient-specific patterns

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Summary

Variety of instruments validated since 1990; majority have included biomarkers

FFQ most commonly used instrument

Wide range of correlation values between the FFQ and biomarkers and other instruments