Assessment of nutritional intake.

The measurement of habitual food and energy intake in man is one of the hardest tasks a physiologist can undertake. There are three basic problems: firstly, the accurate determination of the subject’s customary intake; secondly, the conversion of this information to energy and nutrient intakes; and, thirdly, the length of time food intake should be measured before the information obtained can be said to be a true reflection of habitual food intake. By ‘habitual’ is meant the food an individual normally consumes to provide the energy and nutrient requirements for his everyday activities (Acheson et al. 1980). One of the most important points is that the objective of any study for which dietary information is desired must be clearly defined. Objectives can include: screening for malnutrition; assessing average intakes to compare with, or estimate, average requirements; or, assessing the normal range of intakes compatible with health. There are certain features desirable in a dietary survey method (Nelson 8z Nettleton, 1980): I . Accuracy of individual measurements 2 . Ease of recording 3. The least subject motivation required 4. High co-operation rate in a random sample. There is no generally accepted method of measuring dietary intake of free-living individuals, but there are three methods most commonly used. These are: dietary recall; weighing and recording of food as eaten; and, the analysis and bomb calorimetry of duplicate meals. This paper will describe each method in turn, with a discussion of the limitations and advantages of each.