| Food Composition Data: A User's Perspective (1987) |
|The uses of food composition data|
|Food composition -a key to dietary appraisal and improvement in the United States|
Approaches to meeting data needs
HNIS attempts to meet most of these needs through its publications and computerized data tapes. Agricultural Handbook No. 8 was published in a single volume in 1963, and is being revised in 23 sections, each dealing with one group of foods . Each section contains tables giving representative values of the edible parts of a pound of food as purchased, or 100-gram portions of edible food, and of food by household measures. These tables cover food in its raw state, food as it is processed for market, and food as it is prepared for consumption. Mixtures as marketed and certain commonly used home-prepared mixtures are included. The tables show the number of samples and the standard error for each value. If analytical data are not available, the tables do not show a value.
Data are shown for moisture, energy, protein, total lipid, carbohydrate, crude fibre, ash, dietary fibre (insoluble), calcium, iron, magnesium, phosphorus, potassium, sodium, copper, manganese, zinc, ascorbic acid, thiamine, riboflavin, niacin, vitamin A, pantothenic acid, vitamin B6, folacin, vitamin B12, tocopherol, cholesterol, commonly occurring fatty acids, pytosterol, and amino acids. The published sections of Agriculture Handbook No. 8 present detailed information in a complex format designed to be useful to scientists. Its loose-leaf format allows information for a single food to be updated. Selected data are presented in ways that are more easily used by educators and the general public.
The tables of nutrient data are also available in machine-readable form from the National Technical Information Service, US Department of Commerce. Imputed values for nutrients for which analytical data are not available are given in special data files that represent the staff's best judgement based on analyses of other forms of the food or of similar foods. Such values are flagged on the tape. The Nutrient Data Bank also contains data separately for foods with different characteristics, some of which are not shown separately in the tables. Specific values can be made available on request.
HNIS does not attempt to estimate the levels of pesticides, residues, toxicants, and additives in foods, except those additives that contribute energy and nutrients. The Agency does not have its own laboratories for conducting special-purpose analyses. Certain other parts of USDA, mainly ARS and FSIS, do have such laboratories, which they use to meet their need for highly precise data.
Food composition data have come a long way since the Second World War years when the content of a few nutrients in the civilians' share of the food supply was calculated in USDA on a clanking calculator. This is to the credit of many: the HNIS Nutrient Data Research Branch and their extra-mural analytical programme, the ARS Nutrient Food Composition Laboratory, the food industry, and others who develop sound analytical methods and conduct analyses and share them for use in the Nutrient Data Bank. But there is more to be done. Some HNIS objectives are as follows:
1. Improve nutrient data documentation by implementing an objective system for evaluating and specifying the quality of the data presented.
2. Improve data bases for several food components - dietary fibre, carotenes, loco pherol, selenium, copper, manganese, folacin, chromium, and molybdenum.
3. Keep up with the food production, marketing, and consumption changes in the country by covering new foods and determining the effects of new procedures on nutrient levels.
4. Complete a computerized food formula (recipe) file to develop and document the nutrient content of home-made mixtures and to approximate ingredients in commercial mixtures in the data sets for use in national surveys. This file can be used to assess diets reported in surveys in terms of the basic foodstuffs they contain.
5. Develop guidelines for the proper selection and use of food composition data for a variety of purposes.
6. Encourage users to evaluate carefully the computerized data files they use.
7. Design tools for helping the public to understand that food composition information is useful in selecting nutritious and healthful diets.