Dietary Reference Intakes Research Synthesis Workshop Summary (2007) / Chapter Skim
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5 Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids
5 Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids
Pages 49-60
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From page 49... ...
(Vitamin C was not covered because of time limitations.) She also addressed consistency of the research recommendations with public health concerns, methods to address research recommendations in future DRIs, and the use of Adequate Intakes (AIs)
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From page 50... ...
The ongoing Selenium and Vitamin E Chemoprevention Trial (SELECT) , a very large cancer prevention clinical trial involving 35,000 men, will provide much needed clinical data on possible roles of selenium in disease prevention and on adverse effects that may occur with selenium supplementation.
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From page 51... ...
addressed efficacy of the selenium supplementation as a function of baseline selenium status. Although the investigators found reductions in incident cancer among subjects in the first and second tertiles of selenium intake at entry (both of which represented low selenium intakes because participants for this study were recruited from low-selenium regions of the United States)
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From page 52... ...
Progress Made Over the past few years, much research attention has been given to vitamin E with regard to basic science progress (ongoing stable isotope studies, for example, will greatly illuminate understanding of metabolism and kinetics for vitamin E) , chronic disease studies (especially coronary heart disease prevention studies in high-risk populations)
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From page 53... ...
Dr. Mayne raised a new question in terms of research challenges; namely, When conducting prevention trials, is it more informative to base the research design on unexpected results from previous trials or to base them on findings from observational epidemiology?
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From page 54... ...
The Age-Related Eye Disease Study (AREDS) , a randomized clinical trial using antioxidant nutrients and zinc, found that this nutrient combination significantly reduced the risk of advanced macular degeneration among persons who already had some macular changes (Age-Related Eye Disease Study Research Group, 2001)
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From page 55... ...
The predictive ability of macular pigment for future disease risk is still unknown -- a causal link has not yet been established. Continuing Research Gaps Continuing research gaps include the following: • The dose-dependence of carotenoid effects on health • Effects of polymorphisms in antioxidant-related or regulated genes on the efficacy of antioxidant nutrients • The role of oxidative stress in chronic disease • Predictive value of markers of oxidative stress for clinical end points • Understanding subgroup effects, especially smoking, which are evident throughout the antioxidant nutrient literature Development and validation of biomarkers of oxidative stress are still lacking.
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From page 56... ...
There is a lack of congruity between the public health priority (which is the prevention of chronic diseases) and the current DRI process (which says that a functional indicator is needed to set an EAR or AI)
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From page 57... ...
This would cover the entire population but would not be near the UL. For vitamin E, for example, the values would be as follows: - EAR, 12 mg for adult males - Current RDA, 15 mg - Proposed RDA (EAR plus four standard deviations)
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From page 58... ...
• Are separate UL values needed for different forms of a nutrient? Examples include alpha- and gamma-vitamin E and forms of se lenium such as selenized yeast, sodium selenide, sodium sele nate, and sodium methionine.
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From page 59... ...
59 VITAMIN C, VITAMIN E, SELENIUM, AND CAROTENOIDS DISCUSSION Discussion centered on concerns related to setting the EAR for vitamin E based on vitamin E concentrations and hydrogen peroxide-induced hemolysis -- even though such hemolysis is not a clinical problem. This was the indicator for which data were available; there were insufficient data about other indicators and chronic disease end points that had been considered by the panel.
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