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9 Dietary Reference Intakes for Infants and Children
Pages 95-112

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From page 95...
... Lindsay H Allen of the Western Human Nutrition Research Center at the University of California, Davis, who served on the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and is a former Food and Nutrition Board member, addressed major issues related to setting DRIs for infants and children.
From page 96...
... One serious problem is the accuracy of the data on human milk composition. The reported nutrient values for human milk vary widely among and within different studies.
From page 97...
... When appropriate data were available, the AI was obtained by adding the estimated mean intake of the nutrient from solid food to the amount of that nutrient provided by 600 mL of breast milk. Dietary data on nutrients from solid foods were unavailable for many of the nutrients.
From page 98...
... . Growth factors were based on the approximate proportional increase in protein requirements for growth (FAO/WHO/UNU, 1985)
From page 99...
... . Most of the ULs for children were obtained by extrapolating the adult UL value down, based on body TABLE 9-1 Extrapolations: Different Approaches Actual Reference Metabolic Energy Interpolated Weight Weight Weight Canada/United X X X States Caribbean X Germany/Austria/ ?
From page 100...
... For infants and children, the UL is very close to the AI -- particularly for vitamin A and zinc. Problems Identified Upon Applying Selected Dietary Reference Intakes Inconsistencies Table 9-2 identifies nutrients for which the recommended intakes for 7- to 12-month-old infants are higher than those for 1- to 4-year-old children.
From page 101...
... Table 9-4 shows how the intake range for dietary fiber compares with the AI, by age group. Notably, the upper end of each range of reported intake is far below the AI.
From page 102...
... For example, 90 percent of formula-fed infants ages 0 through 11 months exceed the UL for zinc, and 39 percent exceed the UL for vitamin A High percentages of children ages 1 to 4 years exceeded the UL for zinc, vitamin A, and sodium, but less than 1 percent exceeded the UL for other nutrients.
From page 103...
... by accelerator mass spectrometry. • Stable isotope studies could be used for several purposes, includ ing the following: To estimate the percent absorption from breast milk and food − To conduct kinetic modeling (this requires a time series; for − example, Haskell et al.
From page 104...
... Macronutrients Dr. Allen considers it feasible, timely, and important to address major knowledge gaps identified in the DRI Macronutrients Report (IOM 2002/2005)
From page 105...
... related to biomarkers that are validated in children • Studies with stable isotopes and nanotracers to determine vita min and mineral bioavailability, kinetic studies, and possibly change in pool size on different vitamin intakes • Doubly labeled water studies to measure energy expenditure and water turnover • Determination of vitamin D requirements based on relationships of intake with 25-(OH) D, parathyroid hormone, bone markers, and so on Although measuring food intake by infants and children is difficult, children need their own evidence-based DRIs.
From page 106...
... Some of that zinc is reabsorbed, and some passes out into the stool. Urinary zinc content does not reflect dietary zinc intake.
From page 107...
... Such measurements include the following: • Fractional absorption -- the proportion of ingested zinc that actu ally is getting into the system • The excretion of endogenous zinc secreted into the GI tract • Estimated size of the rapidly exchanging pool, which makes up about 10 percent of total body zinc Despite considerable progress, much work still is needed in terms of validating what the findings really represent in terms of zinc status. Stable Isotope Methodological Considerations Historically, studies have posed many difficulties, two of which are collecting sufficiently large urine samples and complete fecal samples from infants, and avoiding contamination.
From page 108...
... Fecal monitoring with an isotope of zinc plus the rare earth element dysprosium now makes it possible to measure the completeness of the fecal collection and also to obtain fractional absorption from a fecal sample more easily, without a requirement for an intravenous dose. Moreover, by using dysprosium in combination with isotopes and obtaining partial fecal and spot urine collections for 4 to 5 days, the endogenous fecal zinc excretion can be estimated.
From page 109...
... 0 0 3 6 9 AI Ingested Zn (mg/d) FIGURE 9-2 Zinc intake versus absorbed zinc in infants ages 2–4 months: Saturation response model.
From page 110...
... homeostatic mechanisms were not enough to compensate for their low zinc intakes, (2) there is reason to suspect zinc deficiency, and (3)
From page 111...
... BM + Cereal BM + Beef EAR + Physiologic requirement 0 0 1 2 3 4 5 6 7 8 9 Ingested Zn (mg/d) FIGURE 9-4 Absorbed zinc versus zinc intake at age 7 months: implications for complementary foods for breast-fed infants.
From page 112...
... The application of stable isotopes to zinc homeostasis in infants and children suggest that • absorption is characterized by a saturation–response model, • the most important factors influencing zinc absorption are the quantity of zinc ingested and likely phytate (but not host status) , • homeostatic responses are insufficient to prevent dietary defi ciency, and • comparison of population intake to the current EAR for zinc seems to predict a response to interventions.


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