Metrological issues for food consumption data.

1. Metrological issues for food consumption data. Max FeinbergINRA. Mét@riskfeinberg@inapg.inra.fr

2. Using nutritional measurements to study the potential link between nutrition and disease and find methods to prevent the disease. • The best the measurements, the best the decisions… Nutritional epidemiology

3. Exposures = ai  A  Foods Weights pi Consumptions Contents qj  Consumers cij Foods i : individual (household)j : food (group) General nutritional measurement

4. Foods Weights pi Consumptions Consumers cij Consumption measurement

5. 24-hour Recall (24R) • Attempt to define and quantify food intake during a specific day. • Dietary Records (DRs) • Detailed descriptions of types and amounts of foods and beverages consumed, meal by meal, over a prescribed period (3-7 days). • Food Frequency Questionnaires (FFQ) • Long-term diet over months or years, not just a few days. • Household Budget Survey (HBS) • Estimation of the average consumption of a population based on point estimates of food consumptions. • Total Diet Study (TDS) • Estimation of consumer exposure to contaminants based on the analysis of foods « as consumed ». • … Consumption measurements (2)

6. Individualconsumptionscij Weights pi Householdconsumptionsmkj Direct methods Purchasing panels Degradation ?? i : individualsk :householdsj : foods Consumptionshj National budget Survey reduction

7. Uncertainty and variability A proposal to evaluate nutritional measurement quality

8. Metrology: field of knowledge concerned with measurement. • Metrology includes all theoretical and practical aspects of measurement, whichever the measurement uncertainty and field of application. • Measurand: quantity intended to be measured. • Uncertainty (of measurement): parameter that characterizes the dispersion of the quantity values that are being attributed to a measurand, based on the information used. International Vocabulary of Metrology

9. ReportedValue Y True Value T + Y T + Measurandy 95% of replicates in the interval Does this interval representuncertainty? Analogy with chemical measurement

10. Milieu Method Manpower Instrument Material Method Environment Personnel Calibration Result +Uncertainty Traceability Samples handling Equipment Sampling Sources of uncertainty in analysis

11. B1 Day 1 Day 1 B2 Day 2 + yij + B1 B3 B2 B3 Day 3 + Day 3 + Standard deviation of:reproducibility Day 2 Vary sources of uncertainty

12. ReportedValue Composed standard uncertainty True Value + Y T Expanded uncertainty U = kuc(Y) p = 95% k = 2 p = 99% k = 3 95% of the future measurements Measurand Standard and expanded uncertainty

13. Instrument Milieu Individual Material Food Naming Age,Social category, … Grouping Culture ? Weight Size Competence Location Duration Selection Inquirer Panel Study Method Manpower Grouping Measurement +Uncertainty Uncertainty sources for nutritional measurements

14. Use multivariate techniques to identify consumption systems Consumptionsystem Consumptionpattern Variability = + Individual + Uncertainty Consumption pattern

15. Simulated consumption systems

16. Needs for harmonisation. • Data collection procedures. • Data evaluation. • Identification of bias. • How far are methods complementary? • A proposal:use uncertainty-variability approach to organise harmonisation. • A new discipline: “Consumetrics” ? Conclusions