Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000) / Chapter Skim
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3 Vitamin C, Vitamin E, Selenium, and ß-Carotene and Other Carotenoids: Methods
3 Vitamin C, Vitamin E, Selenium, and ß-Carotene and Other Carotenoids: Methods
Pages 58-72
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From page 58... ...
Basic biological research often involving animal models, provides crucial information on mechanisms that may link nutrient consumption to beneficial or adverse health outcomes. Clinical and epiclemiological observational studies likewise play a valuable role in generating and testing hypotheses concerning the health risks and benefits of nutrient intake patterns.
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From page 59... ...
Such ciata were considered in the DRI process and were given particular attention in the absence of reliable ciata with which to directly relate nutrient intake to disease risk. Observational Studies In comparison, observational epidemiological studies are frequently of direct relevance to free-living humans but lack the controlleci setting of human fouling studies.
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From page 60... ...
In addition, there maybe systematic bias in nutrient consumption estimates from self-reports because the reporting of food intakes and portion sizes may clepenci on incliviciual characteristics such as body mass, ethnicity, and age. For example, total energy consumption may tend to be substantially underreporteci (30 to 50 percent)
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From page 61... ...
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 regarding causal relationships between particular exposures and disease outcomes.
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From page 62... ...
The characteristics examined inclucleci the study design and the representativeness of the study population; the validity, reliability, and precision of the methods used for measuring intake and indicators of acloquacy or excess; the control of biases and confouncling factors; and the power of the study to demonstrate a given difference or correlation. Publications solely expressing opinions were not used in setting DRIB.
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From page 63... ...
3. The presence of a clinically important deficiency disease or nutritional syndrome that has been clemonstrateci to relate specifically to an inacloquate intake of the nutrient reviewoci this pathway is facilitated by considering intakes needed to ensure adequate body stores or reserves of the nutrient or of pertinent compounds that the body produces in response to acloquate intake of the nutrient.
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From page 64... ...
Ages O through 6 Months To derive the AI value 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) an average volume of milk intake of 0.78 L/ciay.
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From page 65... ...
Because vitamin C is a water-soluble vitamin and boys have a larger lean body mass and total body water than girls, the adult EAR was acljusteci for children and adolescents on the basis of clifferences in reference weights from Table 1-1. For vitamin E and selenium, the EAR has been extrapolated clownwarci using an adjustment for metabolic body size and growth.
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From page 66... ...
. TABLE 3-1 Estimated Growth Factor by Age Group Age Group Growth Factor 7 mo-3 y 4-8 y 9-13 y 14-18 y Males Females 0.30 0.15 0.15 0.15 0.0 SOURCE: Proportional increase in protein requirements for growth from FAD/WHO/ UNA (1985)
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From page 67... ...
For vitamin E and selenium, analytic methods to cletermine the content of the nutrient in food have serious limitations, the specifics of which are cliscusseci in Chapters ~ through 8. Me th o ~ o flogs ca i Co ns i d era ti o ns The quality of nutrient intake data varies widely across studies.
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From page 68... ...
, and fat intake (which serves as a major carrier for vitamin E) is likely to be more unclerreporteci than energy intake in the Third National Health and Nutrition Examination Survey (NHANES III)
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From page 69... ...
DIETARY INTAKES IN THE UNITED STATES AND CANADA Sources of Dietary Intake Data The major sources of current clietary intake ciata for the U.S. population are the Third National Health and Nutrition Examination Survey (NHANES III)
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From page 70... ...
Data on supplement intake obtained from NHANES III were reported as a part of total nutrient intake (Appenclix C)
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From page 71... ...
1997. Dietary methods research in the Third National Health and Nutrition Examination Survey: Underreporting of energy intake.
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From page 72... ...
The relation between energy intake derived from estimated diet records and intake determined to maintain body weight.
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