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ALTERNATIVES TO DUPLICATE DIET METHODOLOGY
Citation:
Melnyk, L J., M R. Berry Jr., J. R. Tomerlin, L. Barraj, AND S. M. Gordon. ALTERNATIVES TO DUPLICATE DIET METHODOLOGY. Presented at ISEA Annual Meeting, Vancouver, Canada, August 11-15, 2002.
Impact/Purpose:
The overall objective of this research is to support NERL's human exposure measurement and exposure modeling efforts by reducing the amount of uncertainty in the dietary measurements critically needed for improved risk assessment. Specifically, the research provides the tools needed to collect and analyze food samples and to design and understand dietary measurements. The current specific objectives are:
1. to investigate more efficient methods for characterizing population exposures in dietary measurements studies (short-term subtask initiated in FY00; extramural);
2. to develop and improve analytical methods for contaminants in composite food samples collected in dietary measurements studies (long-term subtask; in-house);
3. to improve the model and food database system used in measurements studies for estimating dietary exposure and identifying sources (long-term subtask; extramural).
Description:
Duplicate Diet (DD) methodology has been used to collect information about the dietary exposure component in the context of total exposure studies. DD methods have been used to characterize the dietary exposure component in the NHEXAS pilot studies. NERL desired to evaluate its current DD methodology to detemrine if alternative methods could provide 1) the same amount of information for less cost or 2) additional informaiton for approximately the same cost. Four alternatives were formulated for a public workshop to discuss each in detail: 1-- the Cyclic Sub-Portion Duplicate Diet (CSPDD) is intended to greatly reduce the amount of material that is handled during the laboratory phase of a total exposure study. The CSPDD accomplishes this by requiring study participants to collect only a small sub-sample from each food consumed during the day instead of an exact duplicate portion. The CSPDD incorporates detailed food diaries and/or photographic records to record total amount of food consumed. The sampling procedure and subsequent sample analysis is repeated through multiple cycles. 2 -- The sub-Population Duplicate Diet (SPDD) combines a food frequency questionnaire administered to the entire sample population with a standard DD administered to a statistically representative sub-sample of the target population. 3 -- The Targeted Foods Duplicate Diet (TFDD) uses available information to identify "target" foods which are likely to contain the contaminants of interest. The targeted foods are collected separately from non-target foods, and detailed written or photographic records are kept for portion size and food consumption. 4 -- The Total Population Diet (TPD) preselects foods and beverages presumed to be associated with the contaminants of interest. Eligible households are identified, and prescreened by questionnnaire to determine which, of any, of the preselected foods they normally consume. Information is also obtained about the households typical diet. Specific households are directed to prepare, eat and retain individual samples of selected target foods and beverages on the days of the field study. The foods consumed are weighed and the amounts are recorded, as is information about food preparation. Samples are composited according to food groupings (e.g., meats, vegetables) and in proportion to reported portion size, so that relative contribution of specific food groups is possible. The public workshop included the convening of a panel of experts to offer recommendations about which method, if any, to investigate further. In general, the workshop consensus was the current DD methodology has worked well. The workshop thought that the CSPDD alternative might be worth investigating further because of its potential to significantly reduce study costs. The workshop also concluded that the TFDD might have some utility, but only under certain specific study conditions.