Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005) / Chapter Skim
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2 Overview and Methods
2 Overview and Methods
Pages 37-49
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From page 37... ...
Those that provide a specific beneficial role in human physiological processes and health include water, potassium, sodium, and chloride. Sulfate, while essential for specific metabolic functions, can be formed in sufficient quantities from adequate intakes of sulfur-containing amino acids.
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From page 38... ...
Human Feeding Studies Controlled feeding studies, usually in a confined setting such as a metabolic unit, can yield valuable information on the relationship between nutrient consumption and health-related biomarkers. Much of the understanding of human nutrient requirements to prevent deficiencies is based on studies of this type.
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From page 39... ...
In spite of these limitations, feeding studies play an important role in understanding nutrient needs and metabolism. Such data were considered in the DRI process and were given particular attention in the absence of reliable data to directly relate nutrient intake to disease risk.
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From page 40... ...
. In addition, there may be systematic bias in nutrient consumption estimates from self-reports as the reporting of food intakes and portion sizes may depend on individual characteristics such as body mass, ethnicity, and age.
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Also, dietary 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 42... ...
Therefore, many of the questions raised about the requirements for and recommended intakes of these nutrients cannot be answered fully because of inadequacies in the present database. Apart from studies of overt deficiency diseases, there is a dearth of studies that address specific effects of inadequate intakes on specific indicators of health status, and thus a research agenda is proposed (see Chapter 9)
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From page 43... ...
Ages 0 Through 6 Months To derive the AI for infants ages 0 through 6 months, the mean intake of a nutrient was calculated based 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 44... ...
Method for Extrapolating Data from Younger to Older Infants When information is not available on the nutrient intake of older infants, intake data can be extrapolated from young to older infants. Using the metabolic weight ratio method to extrapolate data from younger to older infants involves metabolic scaling but does not include an adjustment for growth because it is based on a value
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From page 45... ...
Energy intake was used as the basis for extrapolation rather than body weight because this method was not used in the nutrients included in the report. Method for Extrapolating Data from Younger Adults to Older Adults For sodium the AI for older adults is extrapolated from younger adults based on the combined average of median energy intakes for
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From page 46... ...
In these cases, the potential increased need for these nutrients during pregnancy is based on theoretical considerations, including obligatory fetal transfer, if data are available, and on increased maternal needs related to increases in energy or protein metabolism, as applicable. Because there was insufficient evidence to suggest that an AI for potassium or sodium during pregnancy should be quantitatively different from that of nonpregnant women and because pregnant women consumed within the energy range of nonpregnant women, an AI was not set differently for pregnant women.
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. DIETARY INTAKES IN THE UNITED STATES AND CANADA Sources of Dietary Intake Data The major sources of current dietary intake data for the U.S.
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From page 48... ...
Both surveys used the food composition database developed by USDA to calculate nutrient intakes (Perloff et al., 1990) and were adjusted by the method of Nusser et al.
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The relation between energy intake de rived from estimated diet records and intake determined to maintain body weight.
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