| Food Composition Data: A User's Perspective (1987) |
|Managing food composition data|
|Managing a nutrient data-base system: meeting users' needs and expectations|
Meeting users' needs and expectations
All users of the nutrient data-base system express the need for: (a) reliable and valid food composition data with (b) easy access in as short a time as possible, (c) reported in the desired form, and (d) at little cost. An unexpressed need for many is one of hand-holding, consultation, education, and encouragement.
Food Composition Table and Software
It has already been shown that food composition data are used for many purposes. It then becomes evident that the degree of precision and accuracy of nutrient data reports is dependent upon the accuracy and completeness of the quantitative and descriptive information provided for analysis. Users of data for clinical research and applications have the greatest need for complete and accurate analyses. Experience indicates that familiarity with the state of knowledge of food composition is necessary during the research planning stages. All too often, dietary intake records have been collected prior to determining the availability of the data for a food constituent. Research activities involving specific food components of current interest may occur far in advance of the acquisition of composition analyses, for example studies of dietary carotene intake. Constituents for which data have recently been requested are beta carotene, total carotenes, retinol, Vitamin K, choline, chromium, iodine, selenium, total sugars, total refined (or added) sugars, individual sugars, all individual fatty acids, and dietary fibre. Values for some of these constituents are included in USDA Handbook No. 8 revisions; however, for a large number of foods as consumed, data for these constituents are not available. These foods include many packaged, processed foods, fast foods, frozen ready-to-eat foods, and bakery products. Food items are added to the data base as requested by users; thus its composition does reflect its users' requirements. The data base at Case Western Reserve University is being updated continuously, with annual updates made available to owners.
In response to data-base owners' inquiries about updating the food table themselves, it is recommended that they use the recipe file software to accommodate those food items specifically for their use. This avoids the problem of overwriting their data in the food table as they receive updated versions.
It is important that users know how unknown nutrient values are accommodated in summaries. The summary reports a flagged nutrient sum if there is a missing nutrient value for one or more food items included for analysis. Additionally, users may be provided with an output format which indicates missing nutrient values for specific foods (fig. 1).
The degree of precision achieved with calculations of summaries is dependent on the precision of the nutrient values stored in the food table and the computer on which the programs are run. Guidelines for precision provided by USDA are used for inclusion of data from other sources. As smaller data bases are used on smaller computers, the degree of precision decreases. At the same time, as fewer food items are included in a data base, more substitutions must be made, thereby reducing the specificity of the reports for dietary intakes . Such data bases may not be satisfactory for individual dietary records or as a generalpurpose tool. These limitations must be understood and used for appropriate applications.
Inquiries have been received about the use of retention factors. The HVH-CWRU Nutrient Data Base does not incorporate retention factors and the issue is handled somewhat ambiguously. For most purposes, it is possible to select edible portions of foods as consumed. The recipe file system allows for coding of the edible portion of each ingredient by using yield factors for preparation and cooking losses. However, another frequent request is for a data base of usual or common portion sizes. No attempts have been made to add these to the food table; however, this feature would be greatly appreciated for food-service and restaurant menu analysis. Planning menus or diets which meet specified nutrient requirements is an expressed need by a few users. The development of this capability is at present being explored as part of a clinical research study.
Ease of Access and Turn-around Time
The two requisites for ease of access and fast turn-around are a readily available computer and user-friendly, interactive processing and query procedures. The UNIX operating system affords an optimal time-sharing environment for direct access by telephone. Response time is fast and ideal for clinical and day-to-day use in practice or educational settings. Coding is still timeconsuming and the most costly activity associated with analysis; it also requires knowledge of foods and nutrient composition.
Smaller data bases with fewer food items require greater coding knowledge, as more judgements regarding substitutions must be made than for larger data bases containing more foods and more adequate descriptive attributes.
Interactive on-line coding is desirable and would be more error-free; this will be implemented as computer time becomes less expensive. Response time, however, must be very short to alleviate boredom and tedium while entering data. For large data sets, batch processing with offline data entry is more practical and less costly.
The most frequent reports requested are listings of foods with summaries of nutrient content and comparison with RDAs. Printed, easily readable formats are provided for verification and are most often used for clinical practice and patient education. Machine-readable formats must be used for computerized statistical analysis. Summaries of nutrient values or percentages of RDA or energy distribution may be aggregated by meal, time, place, food group, or any other set of descriptive features. Nutrients may be reported in ratios, the most common being nutrient/kilocalorie and polyunsaturated/saturated fatty acids. All reports may be produced in printed table or machine readable formats. Under development at the present time are procedures for directing nutrient analysis output into an existing data-base management system. This will facilitate the generation of almost any kind of desired report.
Many nutrient data users have requested that reports include intake evaluations with recommendations for dietary improvement. The provision of these evaluations is not in accordance with the present policy of providing analyses for professionals' interpretation and use.
From the data-base user's point of view the costs are high, while from the manager's point of view charges seem never to be high enough to support continuing maintenance. This includes all of the related activities involved in understanding users' needs, explaining how their expectations can or cannot be met, and the inevitable hand-holding throughout the process as users and the data-base team are educated. The costs to users of the data-base system comprised two major components: (a) the costs of development and maintenance of the food table and software and (b) the computer costs. As hardware has become less expensive and more efficient, development and maintenance activities represent the major portion of expenses.
Justification for the costs of using nutrient data-base systems for clinical research and applications has been difficult, owing to concern about the reliability of food composition data and the problems of obtaining food consumption information.