Metrological issues for food consumption data. Max Feinberg INRA.

Max Feinberg Nutritional epidemiology 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…

Max Feinberg General nutritional measurement i : individual (household) j : food (group) Consumptions  c ij Contents q j A  Weights p i Foods Consumers Exposures = aiai  Foods

Max Feinberg Consumption measurement Consumptions c ij Weights p i Foods Consumers

Max Feinberg Consumption measurements (2) 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 ». …

Max Feinberg Consumption measurements (1) Indirect methods. Collective estimates. Available data. Food budgets. National statistics. Food balance sheets. Survey of household purchases. Long-period recording. Direct methods. Individual estimates. New data. Prospective. Individual food notebooks (3-14 days). Double weighing. Retrospective. 24-hour recalls. Food history (3-7 days).

Max Feinberg Survey reduction i : individuals k : households j : foods Individual consumptions c ij Weights p i Direct methods Degradation ?? Household consumptions m kj Purchasing panels Consumptions h j National budget

Uncertainty and variability A proposal to evaluate nutritional measurement quality

Max Feinberg International Vocabulary of Metrology 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.

Max Feinberg Analogy with chemical measurement 95% of replicates in the interval Does this interval represent uncertainty? Measurand y + YT Reported Value Y + True Value T

Max Feinberg Sources of uncertainty in analysis Personnel Method Environment Equipment Traceability Sampling Samples handling Result + Uncertainty Calibration Instrument Material Method Manpower Milie u

Max Feinberg Vary sources of uncertainty B1B1 B2B2 B3B3 y ij + Day Day 3 Day 2 + Day 1 Day 2 Day 3 B1B1 B2B2 B3B3 Standard deviation of: reproducibility

Max Feinberg Standard and expanded uncertainty Reported Value + True Value Composed standard uncertainty Expanded uncertainty 95% of the future measurements U = k  u c (Y) p = 95% k = 2 p = 99% k = 3 YT Measurand

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

Max Feinberg Consumption pattern Use multivariate techniques to identify consumption systems Consumption pattern Consumption system Individual Uncertainty + + = Variability

Max Feinberg Simulated consumption systems

Max Feinberg Conclusions 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” ?