10 The nutrition handbook for food processors on nutrients within foods, research has expanded towards studying patterns of food intake(Trichopoulos et al, 2000) 2.3 Sources of dietary data As mentioned earlier. food data are often derived from Food Balance Sheets that provide information on food supply at the popula tion level Household Budget Surveys that collect data on food availability in the house- hold, based on nationally representative samples of households the food intake of free-living individuals, over a specified time pena specifically designed Individual Dietary Surveys that provide information on 2.3.1 Food balance sheets The food balance sheets(FBSs)assembled by the Food and Agriculture Organ isation(FAO)describe the current and developing structure of the national dietary patterns, in terms of the major food commodities that disappear from the national markets(www.fao.org).Afoodbalancesheetiscompletedatnationallevel,on he basis of the annual food production, imports and exports, changes in stock and the agricultural and industrial uses within a country. When these have been taken into account, the remaining quantities represent the food that can be assumed to have been available for human consumption in that country(Kelly et al, 1991). Since 1949, FBSs are regularly collected on a world-wide basis and, in spite of their limitations, countries with no routine information on the food consump- tion of their population and those interested in comparing their national dietary patterns with those of other populations have traditionally used them(Helsing, 1995) International comparisons based on the time series FBS data, in conjunction with information from other sources, can help to indicate trends in the food avail able to the overall population of one country in relation to others, and have thus been used for ecological correlations of food patterns with the morbidity and mor tality of nutrition-related diseases. The user of these data, however, should bear in mind their constraints and interpret comparisons with due caution(Southgate, 1991). The accuracy of recording differs considerably between countries and commodities. Although data on their own food production are collected in some countries, these sources of information can be largely under-recorded. Waste and food given to pets may also be sources of error, since they are considerably depen dent on time, cultures and type of commodities. Lastly, the conversion of food- stuffs into nutrient equivalents by the application of factors derived from various ources must be prudently treatedon nutrients within foods, research has expanded towards studying patterns of food intake (Trichopoulos et al, 2000). 2.3 Sources of dietary data As mentioned earlier, food data are often derived from: • Food Balance Sheets that provide information on food supply at the popula￾tion level. • Household Budget Surveys that collect data on food availability in the house￾hold, based on nationally representative samples of households. • specifically designed Individual Dietary Surveys that provide information on the food intake of free-living individuals, over a specified time period. 2.3.1 Food balance sheets The food balance sheets (FBSs) assembled by the Food and Agriculture Organ￾isation (FAO) describe the current and developing structure of the national dietary patterns, in terms of the major food commodities that disappear from the national markets (www.fao.org). A food balance sheet is completed at national level, on the basis of the annual food production, imports and exports, changes in stocks and the agricultural and industrial uses within a country. When these have been taken into account, the remaining quantities represent the food that can be assumed to have been available for human consumption in that country (Kelly et al, 1991). Since 1949, FBSs are regularly collected on a world-wide basis and, in spite of their limitations, countries with no routine information on the food consump￾tion of their population and those interested in comparing their national dietary patterns with those of other populations have traditionally used them (Helsing, 1995). International comparisons based on the time series FBS data, in conjunction with information from other sources, can help to indicate trends in the food avail￾able to the overall population of one country in relation to others, and have thus been used for ecological correlations of food patterns with the morbidity and mor￾tality of nutrition-related diseases. The user of these data, however, should bear in mind their constraints and interpret comparisons with due caution (Southgate, 1991). The accuracy of recording differs considerably between countries and commodities. Although data on their own food production are collected in some countries, these sources of information can be largely under-recorded. Waste and food given to pets may also be sources of error, since they are considerably depen￾dent on time, cultures and type of commodities. Lastly, the conversion of food￾stuffs into nutrient equivalents by the application of factors derived from various sources must be prudently treated. 10 The nutrition handbook for food processors