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Dietary Reference Intakes Research Synthesis Workshop Summary
E
Research Progress Identified by Individuals at the Workshop
For the convenience of the reader, this appendix uses information provided by workshop presenters to indicate progress related to the DRI research agenda. The list, which is derived from slides used in the workshop presentations and organized by DRI report, identifies topics that have been studied since the release of the respective DRI report and includes some current investigations. Nutrients do not appear below if no presenter noted substantial progress for them. Items in the list represent the view of the presenter; they do not represent workshop conclusions.
Calcium and Related Nutrients
Calcium
Adults
Relationship of calcium intake with health outcomes— results from numerous randomized placebo-controlled trials
Dairy foods linked to reduced blood pressure
Small inverse effect of calcium on body weight—several studies
Effect of high calcium intake on first kidney stone and on recurrence
Children
Better definition of the link between calcium intake and absorption, especially in adolescents
Relationships of vitamin D polymorphisms and mineral metabolism
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Early milk consumption linked to reduced fracture risk in girls and in women
Effects of calcium supplementation—results from several intervention trials
Racial differences in bone turnover and calcium metabolism
Vitamin D
Responses of serum 25-hydroxyvitamin D, parathyroid hormone, and non-vertebral fracture to supplementation with vitamin D3—a number of studies
Vitamin D, and serum parathyroid hormone—one study
Vitamin D and bone in adolescents—one study
Magnesium
Magnesium depletion studies in rats
Positive associations between magnesium intake and bone mass and negative associations with diabetes and stroke—several epidemiologic studies
Fluoride
Relationship of elevated fluoride concentrations to bone mineral density and fractures—one study
B Vitamins and Choline
Riboflavin
Intake data from Ireland
Association of riboflavin intake with plasma homocysteine
Role of riboflavin supplementation in cataract prevention
Niacin
Intake data from Ireland
Molecular identification of high- and low-affinity receptors for nicotinic acid
Flushing mechanisms
Effect of niacin on lipid and lipoprotein levels and on glycemic control in persons with diabetes and peripheral arterial disease—randomized trial
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Extended-release niacin and progression of atherosclerosis— double-blind, placebo-controlled study
Pantothenic Acid
Pantothenic acid content of foods and/or vitamins—two studies
Choline
Human data on male/female differences in endogenous synthesis
Human data on functional markers—two studies
Epidemiologic data on risk of birth defects—two studies
Choline-betaine relationship to plasma homocysteine in humans—three studies
Choline content of foods
Biotin
Histone modification by biotin—one study
Holocarboxylase synthetase deficiency and its treatment with pharmacologic doses of biotin—one study
Vitamin B6
Associations of vitamin B6 and inflammation—four studies
Folate
Associations of folic acid fortification with neural tube defects, vascular disease, cancer, cognition, others
Association between homocysteine concentration and serum folate values
Interactions of folate with other B vitamins and choline related to methylation status
Mass spectrometry methods
Depletion–repletion study demonstrating adequacy of Recommended Dietary Allowance (RDA) for folate for young women of all three methyltetrahydrofolate reductase genotypes
Unmetabolized folic acid in serum or plasma—two studies
Vitamin B12
New methods for identifying status—in development
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Plasma homocysteine and methylmalonic acid values consistent with B12 values required to maintain hematological status—one study
Antioxidants
Selenium
Twenty-five genes identified that code for selenoproteins—characterization is in progress
Selenoprotein P as a potential biomarker for selenium status
Effect of baseline selenium status on chemopreventive efficacy
Selenium and Vitamin E Chemoprevention Trial (SELECT)— will provide clinical data on possible disease prevention
Vitamin E
Much basic science progress
Chronic disease prevention studies, especially coronary heart disease prevention in high-risk populations
SELECT (Selenium and Vitamin E Chemoprevention Trial, a second generation trial examining protective effect of vitamin E against prostate cancer)—Is benefit limited to smokers (the only subjects in ATBC Trial)?
Beta-carotene, carotenoids
Dermal carotenoid concentrations as a possible new status indicator
Chronic disease prevention trial information, with most progress in macular degeneration—Age-Related Macular Degeneration (AREDS) II will be the first large controlled trial of lutein/zeaxanthin supplementation
Macular pigment might serve as an intermediate end point—emerging work in measurement and determinants
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Micronutrients
Vitamin A
Effect of vitamin A status on the conversion of plant carotene—one study
The vitamin A activity of plant foods—three studies
Vitamin K
Content in foods
Iron
Classification of iron-loading syndromes involving hepcidin (down regulator of iron transporter)
Zinc
Stable isotope methods in children
Urine measurement of fractional absorption
Fecal monitoring with zinc isotope plus the rare earth element dysprosium
Isotope dilution method to determine endogenous fecal zinc excretion
Partial fecal and spot urine collections
Improved instrumentation—allows lower doses
Zinc homeostasis and requirements for children
factors that affect fractional absorption of zinc and absorbed zinc
absorption and the “saturation response model”
factors influencing zinc absorption (quantities of ingested zinc and phytate)
Macronutrients and Energy
Carbohydrate
Weight gain with added sugars from certain sources—four longitudinal studies
Glycemic effect of the overall diet with respect to diabetes
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Fatty acids
Relationships of n-3 fatty acids to health
Health effects of docosahexanenoic acid (DHA) and eicosapentaenoic acid (EPA)
Fiber
Relationship of high dietary fiber intake to serum C-reactive protein—two studies, one from the National Health and Nutrition Examination Survey (NHANES), one longitudinal
Protein
Linear regression of nitrogen balance data to estimate the adult requirement
Electrolytes and Water
Sodium and Potassium
Efficacy of increased potassium intake, alone and in combination with reduced sodium intake, on preventing stroke—investigator-initiated trial proposed
Main and interactive effects of potassium and sodium intake on bone mineral density—pilot studies underway
Reduction in risk of cardiovascular disease events associated with sodium reduction
Adverse effects of chronic, low-grade metabolic acidosis that results from an inadequate intake of potassium and its bicarbonate precursors—pilot studies underway
Effects of potassium citrate and potassium chloride on blood pressure
Dietary Assessment
Improvements in the DRIs themselves
Some anticipated progress on replacing Adequate Intakes (AIs) with Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs)
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Some anticipated progress on better specifying factors that can alter the requirement or the Tolerable Upper Intake Level (UL) for specific individuals
Improvements in dietary assessment methods
Matching of units in food composition tables to those in DRIs is nearly complete
Automated Multiple Pass Method for obtaining diet recalls appears to reduce underreporting
The combination of diet recall and propensity questionnaire may improve estimates of usual intake
Observing Protein and Energy Nutrition (OPEN) Study has led to better understanding of errors
Some progress made in quantifying intakes from dietary supplements (2 days in NHANES 2007–2008)
National Cancer Institute method developed for estimating the usual intake of foods, should also work for nutrients
Better statistical methods
Iowa State University (ISU) method and software more available
Method for predicting individual usual intake in NHANES 2003–2004
Development of tools to help professionals use DRIs correctly
Some progress in developing and extending software to assist users with new methods
Agricultural Research Service tables report proportions of the population having intakes below EARs, as applicable
Dietary Planning
Determining usual intake distributions of specific population groups in the United States—(What We Eat in America)
Relationship between foods offered and nutrient intake
Some insight from food folate fortification
Food guide development and evaluation
New U.S. food guide
Canada’s food guide under development using a modeling approach
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Application of DRIs for food and supplement labeling—Institute of Medicine report released in 2003, awaiting Food and Drug Administration rule
Communication and education of nutrition professionals regarding correct uses of DRIs
e-learning course available for a fee
various journal articles
DRI Summary Report nearing release
