12 The nutrition handbook for food processors diet and morbidity/mortality data Lagiou et al, 1999)and dietary intakes of addi tives and contaminants 2.3.3 Individual dietary surveys The specially designed individual dietary surveys (IDSs) primarily aim at the col- lection of information on the food intake of free-living individuals over a speci fied period. The individual surveys, when intakes of the subject are recorded as dequately as possible, are expected to provide evidence on the food quantities consumed and to allow the calculation of both the mean and the distribution of food and nutrient intake among the whole or segments of the population The methods used to assess individual intake can be broadly divided into two generic categories(Willett, 1998): Recall methods of sporadic or habitual diet. They can be limited to the pre vious 24 hours(24-hour dietary recall), where subjects are asked to recall everything they consumed the previous day, or to a diet history referring to a broader and less precisely defined time period using food frequency methods Record methods of daily intake, where subjects are required to keep records of everything they eat and drink for one(24-hour food record) or more days The 7-day weighed record is the one commonly used The quantification of foods consumed and the selection of items to be included in the food list, in the case of closed lists, are critical components of data col lection. standard. natural and household units three-dimensional food model photographs, drawings of foods and geometric shapes are often used for docu henting portion sIzes. Recall methods, in comparison to the record ones, do not require literacy; they re not expected to cause alterations in the eating behaviour of the subject, since the information is collected after the fact; and they have minimal respondent burden. Nevertheless, recall methods are subject to respondents'memory, a limi- tation not present in food records. In recent surveys, dietary recalls are collected using computer software programmes that allow data to be uniformly collected by prompting interviewers to ask all the necessary questions, and may further reduce the cost of data collection and processing. The food records and the 24-hour recall may be used to estimate the absolute intake of energy, macronutrients and some vitamins and minerals that are com- monly found in the food supply. Both methods are frequently used in describing the mean intake of aggregated food groups and in validating food frequency ques tionnaires. These short-term methods are completely open ended, they accom- modate any food or food combination reported by the subject and they allow recording information at various levels of detail including the type of food, the food source, the food processing and preparation methods. They are therefore particularly useful for estimating intakes of culturally diverse populations. One gle day of intake, however, is highly unlikely to be representative of usualdiet and morbidity/mortality data (Lagiou et al, 1999) and dietary intakes of addi￾tives and contaminants. 2.3.3 Individual dietary surveys The specially designed individual dietary surveys (IDSs) primarily aim at the col￾lection of information on the food intake of free-living individuals over a speci- fied period. The individual surveys, when intakes of the subject are recorded as adequately as possible, are expected to provide evidence on the food quantities consumed and to allow the calculation of both the mean and the distribution of food and nutrient intake among the whole or segments of the population. The methods used to assess individual intake can be broadly divided into two generic categories (Willett, 1998): • Recall methods of sporadic or habitual diet. They can be limited to the pre￾vious 24 hours (24-hour dietary recall), where subjects are asked to recall everything they consumed the previous day, or to a diet history referring to a broader and less precisely defined time period using food frequency methods. • Record methods of daily intake, where subjects are required to keep records of everything they eat and drink for one (24-hour food record) or more days. The 7-day weighed record is the one commonly used. The quantification of foods consumed and the selection of items to be included in the food list, in the case of closed lists, are critical components of data col￾lection. Standard, natural and household units, three-dimensional food models, photographs, drawings of foods and geometric shapes are often used for docu￾menting portion sizes. Recall methods, in comparison to the record ones, do not require literacy; they are not expected to cause alterations in the eating behaviour of the subject, since the information is collected after the fact; and they have minimal respondent burden. Nevertheless, recall methods are subject to respondents’ memory, a limi￾tation not present in food records. In recent surveys, dietary recalls are collected using computer software programmes that allow data to be uniformly collected, by prompting interviewers to ask all the necessary questions, and may further reduce the cost of data collection and processing. The food records and the 24-hour recall may be used to estimate the absolute intake of energy, macronutrients and some vitamins and minerals that are com￾monly found in the food supply. Both methods are frequently used in describing the mean intake of aggregated food groups and in validating food frequency ques￾tionnaires. These short-term methods are completely open ended, they accom￾modate any food or food combination reported by the subject and they allow recording information at various levels of detail including the type of food, the food source, the food processing and preparation methods. They are therefore particularly useful for estimating intakes of culturally diverse populations. One single day of intake, however, is highly unlikely to be representative of usual 12 The nutrition handbook for food processors