Medical brain notes 38

  Food Composition Introduction   Although the amount, quality and availability of food composition data vary among countries and regions, in general most developing countries still do not have adequate and reliable data. This is despite the fact that the components of specific foods have been published for over 150 years. Over time food composition data have assumed more scientific, academic, and political importance owing to their utility. Refer to Table 11.1 for practical examples of the uses of food composi-tion data. It was only in 1961 that a regional food composition table was developed and published for Latin America, followed by a food composition table for Africa (1968), the Near East (1970), and Asia (1972). The data in these tables were based on a very limited number of samples, a limited number of nutrients and, in today’s terms, outdated analytical methodologies. However, these tables are still being used today as there are limited up-to-date tables avail-able. W...

  Foods Food composition tables normally consist of a list of selected foods with data on the content of selected nutrients in each food. For a food composition table to be of value in estimating nutrient content, a significant portion of the foods consumed by the group or indi-vidual being studied, as well as the nutrients of interest, should be present in the table. To a large extent this relationship is critical in determining the quality of the information obtained by using the tables, assuming that the data in the tables are of a desirable quality.   Criteria for inclusion in tables The identification of potential contributions of foods to the diet of the population group being studied is unquestionably the first step in identifying and select-ing which foods should and should not be included in the production of a database. However, common sense dictates that it is unreasonable to expect that all foods consumed by all individuals at all times be included in a specific fo...

  Nutrients, nonnutrients and energy Analytical methods Judgment should be made on the availability of suit-able methods of analyses for nutrients and whether the resources, laboratory equipment, and experience are adequate before deciding which nutrients should be included in a nutrient database. If the methods available are not well developed, one should recon-sider the importance of the nutrient and whether it justifies using limited resources, in most instances and countries, to develop the method and train the staff accordingly. It will not be cost-effective to analyze food for a particular nutrient, however high in prior-ity, if methods yield conflicting values. This implies that, as new or improved methods for measuring a nutrient emerge, foods that are important in the food supply and are known or suspected to be a good source of that nutrient should be analyzed or re-analyzed. Food regulation sometimes limits the choice of methods.   The choice of method selected shou...

  Information required on sources of data in tables It is important to have information on the source of the data in a food composition table to be able to check its appropriateness for the study and to confirm its authenticity. The four major categories of sources of data are: ● primary publications, e.g., peer-reviewed articles in scientific literature   ● secondary publications, e.g., reviews or published compilations with compositional data   ● unpublished reports ranging from analytical records to documents prepared with limited circulation, e.g., confidential reports for clients or internal use within a company   ● unpublished analytical data that can be either spe-cifically commissioned analyses for the generation of nutrient data or analytical data that were not particularly generated for the purpose of generat-ing food composition data. Data in food composition tables may be original analytical values, imputed, calculated, or borrowed. Original analytical va...

  Overcoming the inadequacies of food composition tables   Nutrient losses and gains during food processing and preparation   In the absence of analytical data for all forms of foods nutrient values can be estimated by calculation using standard algorithms that have been experimentally derived. Since the content of nutrients per unit mass of food changes when foods are prepared, such losses and gains can be classified in two ways. The first can be described by a food yield factor, when the weight of the primary ingredients at the precooking stage is compared with the weight of the prepared food at the cooking stage and also with the final weight of the food as consumed at the post-cooking stage. The weight of the food can be increased due to the hydra-tion of the dry form of a food (e.g., rice, macaroni) with cooking liquid, (e.g., water or broth) or increased due to the absorption of fat during frying of the food (e.g., potato). Alternatively, the weight of the food can ...