Elizabeth A Yetley's research while affiliated with National Institutes of Health and other places

Publications (109)

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Background Dietary exposure assessments are a critical issue in evaluating human nutrition studies; however, nutrition-specific criteria are not consistently included in existing bias assessment tools. Objective Our objective was to develop a set of Risk of Bias (RoB) tools that integrated nutrition-specific criteria into validated generic assessm...
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Objectives To develop and validate a set of 3 quality assessment instruments (QAls) for evaluating the quality of nutrition studies, for each of the commonly used study designs: (1) randomized controlled trials (RCTs), (2) prospective cohort, and (3) case-control studies. Methods The QAI development and validation process included 8 steps: 1) iden...
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Surrogate biomarkers for clinical outcomes afford scientific and economic efficiencies when investigating nutritional interventions in chronic diseases. However, valid scientific results are dependent on the qualification of these disease markers that are intended to be substitutes for a clinical outcome and to accurately predict benefit or harm. I...
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Background: Public health concerns with regard to both low and high folate status exist in the United States. Recent publications have questioned the utility of self-reported dietary intake data in research and monitoring. Objectives: The purpose of this analysis was to examine the relation between self-reported folate intakes and folate status bio...
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For the past 45 y, the National Center for Health Statistics at the CDC has carried out nutrition surveillance of the US population by collecting anthropometric, dietary intake, and nutritional biomarker data, the latter being the focus of this publication. The earliest biomarker testing assessed iron and vitamin A status. With time, a broad spectr...
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Dietary Reference Intakes (DRIs) are used in Canada and the United States in planning and assessing diets of apparently healthy individuals and population groups. The approaches used to establish DRIs on the basis of classical nutrient deficiencies and/or toxicities have worked well. However, it has proved to be more challenging to base DRI values...
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Background: Folate cutoffs for risk of deficiency compared with possible deficiency were originally derived differently (experimental compared with epidemiologic data), and their interpretations are different. The matching of cutoffs derived from one assay with population-based data derived from another assay requires caution. Objective: We asse...
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Background: Temporal trends in the US population's vitamin D status have been uncertain because of nonstandardized serum 25-hydroxyvitamin D [25(OH)D] measurements. Objective: To accurately assess vitamin D status trends among those aged ≥12 y, we used data from the cross-sectional NHANESs. Design: A liquid chromatography-tandem mass spectrome...
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Adequate folic acid intake is an effective dietary-based prevention tool for reducing the risk of neural tube defects. Achieving adequate intake for the prevention of neural tube defects frequently requires the consumption of foods fortified with folic acid and/or the use of folic acid-containing dietary supplements. To date, research on the potent...
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Background: The 2007-2010 NHANES provides the first US nationally representative serum 25-hydroxyvitamin D [25(OH)D] concentrations measured by standardized liquid chromatography-tandem mass spectrometry. Objective: We describe patterns for total 25(OH)D and individual metabolites in persons aged ≥1 y stratified by race-ethnicity and grouped by...
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Background: Serum concentrations of 25-hydroxyvitamin D (25OHD) were measured for the National Health and Nutrition Examination Survey (NHANES) over the 1988-2006 period using a radioimmunoassay (RIA). In 2010, the Centers for Disease Control and Prevention (CDC) reissued RIA-harmonized 25OHD for NHANES 2004 and 2006, and advised users to adjust t...
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Serum and erythrocyte (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured the serum folate forms (5-methyltetrahydrofolate (5-methylTHF), unmetabolised folic acid (UMFA), non-methyl folate (sum of tetrahydrofolate (THF), 5-formyltetrahydrofolate (5-formylTHF), 5,10-met...
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Serum total folate consists mainly of 5-methyltetrahydrofolate (5-methylTHF). Unmetabolized folic acid (UMFA) may occur in persons consuming folic acid-fortified foods or supplements. We describe serum 5-methylTHF and UMFA concentrations in the US population ≥1 y of age by demographic variables and fasting time, stratified by folic acid-containing...
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The discrepancy between the commonly used vitamin D status measures-intake and serum 25-hydroxyvitamin D [25(OH)D] concentrations-has been perplexing. Sun exposure increases serum 25(OH)D concentrations and is often used as an explanation for the higher population-based serum concentrations in the face of apparently low vitamin D intake. However, s...
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No consensus exists about which cutoff point should be applied for serum vitamin B-12 (SB-12) concentrations to define vitamin B-12 status in population-based research. The study's aim was to identify whether a change point exists at which the relation between plasma methylmalonic acid (MMA) and SB-12 changes slope to differentiate between inadequa...
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Context: A reverse J-shaped association between serum 25-hydroxyvitamin D (25[OH]D) concentration and all-cause mortality was suggested in a 9-year follow-up (1991-2000) analysis of the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994). Objective: Our objective was to repeat the analyses with 6 years additional follo...
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Background: There are questions about the appropriate method for the accurate estimation of the population prevalence of nutrient inadequacy on the basis of a biomarker of nutrient status (BNS). Objective: We determined the applicability of a statistical probability method to a BNS, specifically serum 25-hydroxyvitamin D [25(OH)D]. The ability t...
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The NHANES has monitored folate status of the U.S. population from prefortification (1988-1994) to postfortification (1999-2010) by measuring serum and RBC folate concentrations. The Bio-Rad radioassay (BR) was used from 1988 to 2006, and the microbiologic assay (MBA) was used from 2007 to 2010. The MBA produces higher concentrations than the BR an...
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The NHANES measured serum and RBC folate concentrations by using a radioassay during prefortification (1988-1994) and postfortification (1999-2006) periods followed by the use of a microbiologic assay (MBA) from 2007-2010. The MBA produces higher concentrations than does the radioassay and is considered to be more accurate. To allow for accurate lo...
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A roundtable dialogue to discuss "NHANES Monitoring of Biomarkers of Folate and Vitamin B-12 Status" took place in July 2010. This article provides an overview of the meeting and this supplement issue. Although the focus of the roundtable dialogue was on the measurement of folate and vitamin B-12 status biomarkers in NHANES, this article also descr...
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NHANES measured folate and vitamin B-12 status biomarkers, starting with serum folate from NHANES I (1974-1975) through 2010. Subsequent NHANES measured additional biomarkers [eg, red blood cell folate, serum vitamin B-12, total homocysteine (tHcy), methylmalonic acid, serum folic acid, and 5-methyltetrahydrofolic acid]. Examples of the uses of the...
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Folate status assessments depend primarily on the measurement of biomarkers such as serum and red blood cell folate. Lessons learned from a large national monitoring system such as the National Health and Nutrition Examination Survey and a public health intervention such as the implementation of folic acid fortification in the United States have pr...
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Three laboratories participated with their laboratory-specific microbiologic growth assays (MA) in the NHANES 2007-2008 to assess whether the distributions of serum (n = 2645) and RBC folate (n = 2613) for the same one-third sample of participants were comparable among laboratories. Laboratory (L) 2 produced the highest and L1 the lowest serum and...
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A roundtable to discuss the measurement of folate status biomarkers in NHANES took place in July 2010. NHANES has measured serum folate since 1974 and red blood cell (RBC) folate since 1978 with the use of several different measurement procedures. Data on serum 5-methyltetrahydrofolate (5MTHF) and folic acid (FA) concentrations in persons aged ≥60...
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A roundtable to discuss the measurement of vitamin B-12 (cobalamin) status biomarkers in NHANES took place in July 2010. NHANES stopped measuring vitamin B-12-related biomarkers after 2006. The roundtable reviewed 3 biomarkers of vitamin B-12 status used in past NHANES--serum vitamin B-12, methylmalonic acid (MMA), and total homocysteine (tHcy)--an...
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Various definitions, criteria, tests, and cutoffs have been used to define vitamin B-12 status; however, a need exists for the systematic study of vitamin B-12 status in the United States because of concerns about high folic acid intakes and the potential for associated adverse effects. The objective was to determine the effect of different cutoff...
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This review is a synopsis from a recent symposium entitled "Update on Nutrition Research Methodologies" presented at the American College of Nutrition's Annual Meeting in Orlando, in October 2009. The speakers provided an overview of new handheld and Web-based dietary assessment tools and their application to clinical and epidemiologic studies, ide...
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Key findings: Use of dietary supplements is common among the U.S. adult population. Over 40% used supplements in 1988-1994, and over one-half in 2003-2006. Multivitamins/multiminerals are the most commonly used dietary supplements, with approximately 40% of men and women reporting use during 2003-2006. Use of supplemental calcium increased from 28...
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A roundtable to discuss monitoring of serum 25-hydroxyvitamin D [25(OH)D] in the NHANES was held in late July 2009. Topics included the following: 1) options for dealing with assay fluctuations in serum 25(OH)D in the NHANES conducted between 1988 and 2006; 2) approaches for transitioning between the RIA used in the NHANES between 1988 and 2006 to...
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Unmetabolized serum folic acid (UMFA) has been detected in adults. Previous research indicates that high folic acid intakes may be associated with risk of cancer. The objective was to examine UMFA concentrations in relation to dietary and supplemental folate and status biomarkers in the US population aged > or =60 y. Surplus sera were analyzed with...
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The concentration or threshold of 25-hydroxyvitamin D [25(OH)D] needed to maximally suppress intact serum parathyroid hormone (iPTH) has been suggested as a measure of optimal vitamin D status. Depending upon the definition of maximal suppression of iPTH and the 2-phase regression approach used, 2 distinct clusters for a single 25(OH)D threshold ha...
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The term total folate intake is used to represent folate that occurs naturally in food as well as folic acid from fortified foods and dietary supplements. Folic acid has been referred to as a double-edged sword because of its beneficial role in the prevention of neural tube defects and yet possible deleterious effects on certain cancers and cogniti...
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The methodology used to establish tolerable upper intake levels (UL) for nutrients borrows heavily from risk assessment methods used by toxicologists. Empirical data are used to identify intake levels associated with adverse effects, and Uncertainty Factors (UF) are applied to establish ULs, which in turn inform public health decisions and standard...
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Folate is an essential B vitamin found naturally in a variety of foods such as leafy vegetables, citrus fruits, liver, and lentils. There are many forms of folate, and folic acid is the form used in folate supplements and food fortification. Folate is involved in many reactions requiring the transfer of 1-carbon units, being essential for both DNA...
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The quality of nutrition-related systematic reviews (SRs) is an unstudied but important factor affecting their usefulness. The objectives were to evaluate the reporting quality of published SRs and to identify areas of improvement. Descriptive and exploratory analyses of the reporting quality (7 nutrition items and 28 SR reporting items) of all Eng...
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Recent Institute of Medicine (IOM) reviews of the process for deriving Dietary Reference Intakes (DRIs) suggest that determining the need for a new nutrient review should be evaluated against criteria set a priori. After selecting the criterion of significant new and relevant research, a working group of US and Canadian government scientists used r...
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Systematic reviews represent a rigorous and transparent approach to synthesizing scientific evidence that minimizes bias. They evolved within the medical community to support development of clinical and public health practice guidelines, set research agendas, and formulate scientific consensus statements. The use of systematic reviews for nutrition...
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Changes in serum 25-hydroxyvitamin D [25(OH)D] concentrations in the US population have not been described. We used data from the National Health and Nutrition Examination Surveys (NHANES) to compare serum 25(OH)D concentrations in the US population in 2000-2004 with those in 1988-1994 and to identify contributing factors. Serum 25(OH)D was measure...
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Regulatory officials world-wide are paying attention to the process for establishing the upper level of intake for nutrient substances. The rapidly expanding use of dietary supplements, fortified foods, and functional foods, coupled with increased trade in these products, has focused attention on ensuring their safety and on harmonizing standards i...
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This article describes the information currently available in the National Nutrition Monitoring System that is relevant to assessing the vitamin D status of US population groups, the strengths and limitations of this information, and selected results of vitamin D nutritional status assessments. The National Health and Nutrition Examination Survey (...
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We summarize the discussions of a roundtable following the conference "Vitamin D and Health in the 21st Century: an Update." The roundtable participants offered additional information on vitamin D research needs from a critical, impartial, and interdisciplinary perspective. Although the group recognized the progress to date, they found that the ava...
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We summarize the key findings, strength of the evidence, and research needs identified in the National Institutes of Health conference "Vitamin D and Health in the 21st Century: an Update," which was held in September 2007; a systematic evidence-based review; and a National Institutes of Health roundtable discussion held after the conference by sci...
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This article describes the information currently available in the National Nutrition Monitoring System that is relevant to assessing the vitamin D status of US population groups, the strengths and limitations of this information, and selected results of vitamin D nutritional status assessments. The National Health and Nutrition Examination Survey (...
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Data from the National Health and Nutrition Examination Surveys. Very large increases in blood folate levels of the U.S. population occurred between 1988-1994 and 1999-2000. Small fluctuations in blood folate levels occurred over the time period 1999-2006. The median red blood cell (RBC) folate level of the U.S. population 4 years of age and older...
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The National Health and Nutrition Examination Survey (NHANES) has monitored total homocysteine (tHcy) concentrations in a nationally-representative sample of the US population since 1991. Until recently, however, data could not be compared across survey periods because of changes in analytical methods and specimen matrices. Such an analysis of thes...
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The Nutrient Data Laboratory of the United States Department of Agriculture (USDA) is collaborating with the Office of Dietary Supplements (ODS), the National Center for Health Statistics (NCHS), and other government agencies to design and populate a dietary supplement ingredient database (DSID). This analytically based, publicly available database...
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Although an estimated 50% of adults in the United States consume dietary supplements, analytically substantiated data on their bioactive constituents are sparse. Several programs funded by the Office of Dietary Supplements (ODS) at the National Institutes of Health enhance dietary supplement database development and help to better describe the quan...
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To describe dietary supplement use among US children. Analysis of nationally representative data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES). Home interviews and a mobile examination center. Children from birth through 18 years who participated in NHANES (N=10,136). Frequency of use of any dietary supplement product...
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This article illustrates the importance of having analytical data on the vitamin and mineral contents of dietary supplements in nutrition studies, and describes efforts to develop an analytically validated dietary supplement ingredient database (DSID) by a consortium of federal agencies in the USA. Preliminary studies of multivitamin mineral supple...
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As part of a study initiating the development of an analytically validated Dietary Supplement Ingredient Database (DSID) in the United States (US), a selection of dietary supplement products were analyzed for their caffeine content. Products sold as tablets, caplets, or capsules and listing at least one caffeine-containing ingredient (including bot...
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Monitoring the folate status of US population groups over time has been a public health priority for the past 2 decades, and the focus has been enhanced since the implementation of a folic acid fortification program in the mid-1990s. We aimed to determine how population concentrations of serum and red blood cell (RBC) folate and serum vitamin B-12...
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Evidence-based systematic reviews evaluating dietary intake and nutritional interventions are becoming common but are relatively few compared with other applications. Concerns remain that systematic reviews of nutrition topics pose several unique challenges. We present a successful collaboration to systematically review the health effects of a comm...
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The B vitamin, folate, functions as a coenzyme in single-carbon transfer reactions. Dietary sources include a family of derivatives found naturally in foods and the synthetic form (folic acid) used in fortified foods and dietary supplements. The role of folate in treating and preventing the megaloblastic anaemia of pregnancy has long been recognize...
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700.12 Abstract 700.12 Intakes of antioxidants beta-carotene, vitamins C and E, and selenium can be greater from supplements than from foods, so determination of actual levels in MVMs is important if accurate estimates of exposures are to be possible. We assessed frequency of reported percent Daily Value (%DV) levels in MVMs using NHANES 2001-02 da...
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DSID Overview DSID Overview The Nutrient Data Laboratory (NDL) at the U.S. Department of Agriculture is collaborating with the Office of Dietary Supplements at the National Institutes of Health, the National Center for Health Statistics at the Centers for Disease Control and Prevention, and the National Institute of Standards and Technology (NIST)...
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Although multivitamins, multiminerals, and similar terms (eg, multis or multiples) are commonly used, they have no standard scientific, regulatory, or marketplace definitions. Thus, multivitamins-multiminerals refers to products with widely varied compositions and characteristics. Multivitamin-multimineral composition databases use label values as...
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Regulatory decisions informed by sound science have an important role in many regulatory applications involving drugs and foods, including applications related to dietary supplements. However, science is only one of many factors that must be taken into account in the regulatory decision-making process. In many cases, the scientific input to a regul...