Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001) / Chapter Skim
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2 Overview and Methods
2 Overview and Methods
Pages 44-59
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From page 44... ...
those that lack sufficient evidence of their specific role in human health and lacking a reproducibly observeci human indicator in response to their absence in the cliet. The micronutrients that have a beneficial role in human health include vitamin A, vitamin K, chromium, copper, iodine, iron, manganese, molybdenum, and zinc.
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Human Feeding Studies Controlled feeding studies, usually in a confined setting such as a metabolic ward, can yield valuable information on the relationship between nutrient consumption and health-relateci biomarkers.
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Depletion-repletion studies, by contrast, measure nutrient status while subjects are maintained on cliets containing marginally low or deficient levels of a nutrient; then the cleficit is corrected with measured amounts of that nutrient. Unfortunately, these two types of studies have several limitations: typically they are limited in time to a few clays or weeks, and so longer-term outcomes cannot be measured with the same level of accuracy.
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From page 47... ...
In aciclition, there may be systematic bias in nutrient consumption estimates from self-report as the reporting of food intakes and portion sizes may clepenci on incliviclual characteristics such as body mass, ethnicity, and age. For example, total energy consumption may tend to be substantially underreported (30 to 50 percent)
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From page 48... ...
Also, clietary intervention or supplementation trials tend to be costly and logistically difficult, and the maintenance of intervention adherence can be a particular challenge. Because of the many complexities in conducting studies among free-living human populations and the attendant potential for bias and confounding, it is the totality of the evidence from both observational and intervention studies, appropriately weighted, that must form the basis for conclusions about causal relationships between particular exposures and disease outcomes.
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From page 49... ...
Apart from studies of overt deficiency diseases, there is a dearth of studies that aciciress specific effects of inacloquate intakes on specific indicators of health status, and thus a research agenda is proposed (see Chapter 15~. For many of these nutrients, estimated requirements are baseci on factorial, balance, and biochemical indicator ciata because there is little information relating health status indicators to functional suf~ .
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Ages O through 6 Months To derive the AI for infants ages 0 through 6 months, the mean intake of a nutrient was calculated baseci on (1) the average concentration of the nutrient from 2 to 6 months of lactation using consensus values from several reported studies, if possible, and (2)
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From page 51... ...
the content of the nutrient provicleci by 0.6 L/ciay of human milk, which is the average volume of milk reported from studies of infants receiving human milk in this age category (Heinig et al., 1993)
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If there is a lack of evidence demonstrating an association between metabolic rate and nutrient requirement, neecis are estimated directly proportional to total body weight.
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Setting the To;terab;te Upper Intake [event for Children When ciata are not available to set the Tolerable Upper Intake Level (UL) for children, the UL for adults is extrapolated clown using the reference body weights in Table 1-1: ULchild ULadult X Weightadult/Weightchild.
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Therefore, 16 kg is acicleci to the reference weight for nonpregnant adolescent girls and women for extrapolation. Methods for Determining Increased Needs for Lactation It is assumed that the total nutrient requirement for lactating women equals the requirement for nonpregnant, nonlactating women of similar age plus an increment to cover the amount neecleci for milk production.
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Both surveys used the food composition database developed by USDA to calculate nutrient intakes (Perloff et al., 1990) and were acljusteci by the method of Nusser et al.
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The FDA Total Diet Study utilized a number of FDA Market Basket Surveys collected between the third quarter of 1991 and the first quarter of 1997. An upciateci food map was clevelopeci with use of a total of 306 core foocis to map the USDA food consumption survey ciata for 1994 to 1996.
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Appendix F provides means and selected percentiles of clietary intakes of vitamin A, iron, and zinc for inclivicluals in Quebec and Nova Scotia. Sources of Supplement Intake Data Although subjects in the CSFII (1994-1996)
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1993. Methodological issues in the measurement of cardiovascular risk factors: Within-person variability in selected serum lipid measures Results from the Third National Health and Nutrition Survey (NHANES III)
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The relation between energy intake derived from estimated diet records and intake determined to maintain body weight.
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