Dietary Reference Intakes Research Synthesis: Workshop Summary (2007)

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.

• 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

• 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

• 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 depletion studies in rats

• Positive associations between magnesium intake and bone mass and negative associations with diabetes and stroke—several epidemiologic studies

• Relationship of elevated fluoride concentrations to bone mineral density and fractures—one study

• Intake data from Ireland

• Association of riboflavin intake with plasma homocysteine

• Role of riboflavin supplementation in cataract prevention

• 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

• Extended-release niacin and progression of atherosclerosis— double-blind, placebo-controlled study

• Pantothenic acid content of foods and/or vitamins—two studies

• 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

• Histone modification by biotin—one study

• Holocarboxylase synthetase deficiency and its treatment with pharmacologic doses of biotin—one study

• Associations of vitamin B6 and inflammation—four studies

• 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

• New methods for identifying status—in development

• Plasma homocysteine and methylmalonic acid values consistent with B₁₂ values required to maintain hematological status—one study

• 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

• 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

• Effect of vitamin A status on the conversion of plant carotene—one study

• The vitamin A activity of plant foods—three studies

• Content in foods

• Classification of iron-loading syndromes involving hepcidin (down regulator of iron transporter)

• 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)

• Weight gain with added sugars from certain sources—four longitudinal studies

• Glycemic effect of the overall diet with respect to diabetes

• Relationships of n-3 fatty acids to health

• Health effects of docosahexanenoic acid (DHA) and eicosapentaenoic acid (EPA)

• 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

• Linear regression of nitrogen balance data to estimate the adult requirement

• 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

• Improvements in the DRIs themselves

  • Some anticipated progress on replacing Adequate Intakes (AIs) with Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs)

• 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

• 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

• 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