Dietary Reference Intakes Research Synthesis Workshop Summary (2007) / Chapter Skim
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6 Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silver, Vanadium, and Zinc
6 Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silver, Vanadium, and Zinc
Pages 61-72
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From page 61... ...
Janet Hunt of Grand Forks Human Nutrition Research Center, former member of the Subcommittee on Interpretation and Uses of Dietary Reference Intakes, provided research perspectives related to the report. DISCUSSION OF RESEARCH RECOMMENDATIONS Presenter: Robert M
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From page 62... ...
Insufficient data were available on isotope dilution studies to obtain a good prediction of body stores of vitamin A Neither serum nor plasma retinol concentrations could be used because retinol is under homeostatic control.
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From page 63... ...
These recommendations appear below. These four research recommendations cut across many of the nutrients and remain major research gaps.
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From page 64... ...
End Points that Indicate Nutrient Toxicity A number of functional and biochemical end points that indicate nutrient toxicity offer promising avenues of research: • Iron and oxidative status, iron content of ferritin, and hepcidin • The relationship between iron status, serum ferritin, and the metabolic syndrome and the putative risk for cardiovascular dis eases related to oxidative damage • The examination of which systems become dysfunctional with excess zinc, considering the immune system as a prime target of investigation • The relationship of vitamin A intake with bone demineraliza tion -- Feskanich and coworkers (2002) provide evidence that this adverse effect occurs at intakes that are close to the RDA, but some inconsistent findings also have been reported Interactions Of particular interest are studies of interactions between calcium and zinc and between zinc and phytate.
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From page 65... ...
The investigation of lactating women's iodine requirements is another topic still in need of research. TABLE 6-1 Selected Dietary Reference Intake Values for Vitamin A and the Criteria Used to Set Them, by Life Stage Life Stage Criterion EAR RDA AI UL ←µg of vitamin A/day→ 0–6 months Human milk content 400 7–12 months Extrapolated from 0–6 500 months 1–2 years Extrapolated from adults 210 300 600 4–8 years Extrapolated from adults 275 400 900 9–13 years, M Extrapolated from adults 445 600 9–13 years, F Extrapolated from adults 420 600 14–18 years, M Extrapolated from adults 630 900 14–18 years, F Extrapolated from adults 485 700 > 18 years, M Adequate body stores 625 900 > 18 years, F Adequate body stores 500 700 M = Male; F = Female; EAR = Estimated Average Requirement; RDA = Recom mended Dietary Allowance; AI = Adequate Intake; UL = Tolerable Upper Intake Level.
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From page 66... ...
Russell posed a set of topics for investigation that have arisen since the writing of the DRI Micronutrients Report: • Vitamin A and gene expression profiles, especially gene expres sions that control certain functions • The bioavailability and metabolism of menaquinones and the roles of menaquinones and phyloquinones in sphingolipid me tabolism. Animal data published since the DRI Micronutrients Report completion points to roles for vitamin K in the form of menaquinone for brain function: it stimulates sphingolipid syn thesis and improves cognition.
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From page 67... ...
For vitamin A, there has been substantial progress as well. Despite good progress for iron, much remains to be done, especially regarding hepcidin as a marker of iron status.
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From page 68... ...
In intervention studies in developing countries, this algorithm using TfR and serum ferritin has been very sensitive. In contrast to using hemoglobin as an end point, this algorithm-based method of measuring body iron stores can be used in intervention studies to reduce the number of subjects and shorten the observation time.
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From page 69... ...
This area of research requires more animal as well as human studies to identify sensitive and specific indicators. The few functional indices available do not provide evidence that the use of mineral supplements will affect performance, as concluded in a recent review of mineral requirements for military personnel (IOM, 2006b)
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From page 70... ...
Recognition has increased that the oral zinc dose or the amount of zinc in a meal affects zinc absorptive efficiency (International Zinc Nutrition Consultative Group, 2004)
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From page 71... ...
Step 7: Applying Dietary Reference Intakes in Planning and Assessing Diets Apparent discrepancies have been discovered when applying the new DRIs to the planning and assessment of diets. For example, discrepancies between intakes and the UL for manganese appear for subgroups of individuals.
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From page 72... ...
72 DIETARY REFERENCE INTAKES DISCUSSION Comments and questions following this presentation were of a general nature and are summarized in Chapter 13, "Wrap-up Session."
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