1 Validation of dietary assessment methods present Heather Ward, Natasha Powell, Sheila Bingham, and Kay Tee Khaw, University of Cambridge

2 Search criteria Inclusion criteria English language articles, 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

3 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 = reference lists 82 met inclusion/ exclusion criteria +

4 Biomarkers used in majority of studies 66% validated against biomarkers 34% compared to other reported dietary instruments Methodn Diet diary (DD)28 Diet history (DH)12 Food frequency questionnaires (FFQ) 66 24hour recall (24HR)24 Weighed food record (WFR) 33 Other9

5 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) Methodn Diet diary (DD)28 Diet history (DH)12 Food frequency questionnaires (FFQ) 66 24hour recall (24HR)24 Weighed food record (WFR) 33 Other9

6 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

7 Diverse associations between FFQ and recovery biomarkers 1) Doubly labeled water > FFQ-energy by 22%, r ) 24hr urinary nitrogen vs. FFQ-protein: ‘Incomplete’ urine r – Complete urine r , 31 – r NS  0.27 upon exclusion of incomplete urine 36 3) 24hr urinary potassium vs. FFQ-potassium: Incomplete r NS 34, 35 Complete r < , 25, 27, 28, 31

8 Concentration biomarkers: indicators of intake 1)Plasma βcar vs. FFQ-βcar: r NS 35,41,47 or < , 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 – ,25, 28, 49, 56, 58, 59 Smoking decreases serum ascorbic acid levels Smokers r 0.46, non-smokers r

9 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 – ,67,68 Adipose tissue FA vs. FFQ-FA r 0.15 – , 67,

10 Replacement biomarkers: indicators for difficult-to-quantify nutrients 1) 24hr urinary sodium vs. FFQ-sodium Incomplete, r NS 34,41 Complete, r ) Serum/urinary phytoestrogens vs. FFQ- phytoestrogens and soy-based foods r 0.24 – 0.27, men 76 r 0.28 – 0.74, women 77

11 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

12 FFQ vs. WFR (19 studies) FFQ > WFR in some studies 7,24,37,81,82, but not all 34,54,64,83-86 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

13 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 – 89% classified into same/adjacent quantile by both methods, < 36% extremely misclassified 28,47,74, 91,92

14 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

15 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

16 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