Showing papers by "Michael L. Nelson published in 1989"

Between- and within-subject variation in nutrient intake from

Abstract: ABSTRACI’ In prospective studies ofdiet it is often necessary to know for how many days subjects should record food consumption in order to be able to rank subjects correctly according to their nutrient intakes. Data from six studies-of toddlers, families, schoolchildren, dietitians, pregnant women, and elderly subjects-were analyzed to estimate the number of recording days necessary for energy, 28 nutrients, and the ratio of polyunsaturated to samrated fatty acids (P:S). The most striking finding is that 7 d ofdiet record do not rank subjects with the degree ofaccuracy commonly assumed. For some nutrients, such as iron, zinc, nicotinic acid, and pyridoxine, it may be desirable to record diet over a number of short, separate periods to achieve the number ofdays required. For others, such as copper, retinol, carotene, vitamin B-12, polyunsaturated fatty acids, P:S, and alcohol, alternative methods of assessment based on dietary histories or questionnaires may be more appropriate. Am J C/in Nutr 1989;50: I 55-67.