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Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington (DC): National Academies Press (US); 1998.

Cover of Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline

Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.

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This report is the second in a series that presents a comprehensive set of reference values for nutrient intakes for healthy U.S and Canadian populations. It is a product of the Food and Nutrition Board of the Institute of Medicine (IOM) working in cooperation with scientists from Canada.

The report establishes a set of reference values for the B vitamins and choline to replace previously published Recommended Dietary Allowances (RDAs) for the United States and Recommended Nutrient Intakes (RNIs) for Canada. It considers evidence concerning the prevention of disease and developmental disorders along with more traditional evidence of sufficient nutrient intake; and examines data about choline, a food component that in the past has not been considered essential in the human diet. Although the reference values are based on data, the data were often scanty or drawn from studies that had limitations in addressing the question. Thus, scientific judgment was required in setting the reference values. The reasoning used is described for each nutrient in Chapters 4 through 12. Evidence concerning the use of these nutrients for the amelioration or cure of disease or disability was not considered because that was beyond the project's scope of work.

The B vitamins appear second in the series largely because recommendations for folate intake have been a subject of controversy for many years. The RDA for folate has shifted up and down. Recently, low folate intake has been linked with vascular disease and other chronic conditions as well as risk of neural tube defects and other congenital malformations in the offspring of women of reproductive age. However, high folate intake has also been implicated in delaying the diagnosis of pernicious anemia until after irreversible neurological damage has occurred. A major task of the Panel on Folate, Other B Vitamins, and Choline; the Subcommittee on Upper Reference Levels of Nutrients (UL Subcommittee); and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (DRI Committee) was to analyze the evidence on beneficial and adverse effects of different folate intakes—in the context of setting Dietary Reference Intakes (DRIs) for all the B vitamins and choline.

Many of the questions raised about requirements for and recommended intakes of B vitamins and choline cannot be answered fully because of inadequacies in the present database. Apart from studies of overt deficiency disease, there is a dearth of studies that address specific effects of inadequate B vitamin intakes on health status. For most of the B vitamins, there is no direct information that permits estimating the amounts required by children and adolescents. For five of the B vitamins, data useful for the setting of Tolerable Upper Intake Levels (ULs) are sparse, precluding reliable estimates of how much can be ingested safely. For some of these nutrients, there are questions about how much is contained in the food North Americans eat. Thus, another major task of the report was to outline a research agenda to provide a basis for public policy decisions related to recommended intakes of the B vitamins and choline and ways to achieve those intakes. The process for establishing DRIs is an iterative process and is thus evolving as the conceptual framework is applied to new nutrients and food components. With more experience, the proposed models for establishing reference intakes for use with nutrients and food components that play a role in health will be refined and, as new information or new methods of analysis are adopted, these reference values will be reassessed. The DRI Committee and its UL Subcommittee are developing plans to explore ways to address the safety of high nutrient intakes in other age groups or situations where data are lacking. For example, although the panel chose to use metabolic body weight (kg0.75) as the basis for adjusting all DRIs, including ULs for children for establishing intakes of the vitamins reviewed in this report, the proposed risk assessment model of the UL Subcommittee uses body weight directly as the default for extrapolation to children because of its more conservative result.

Considerations of bioavailability and nutrient-nutrient interactions played a key role in the decision-making process for several B vitamins. For example, the concept of dietary folate equivalents is introduced to help estimate folate requirements, and limitations on the absorption of vitamin B12 were considered when recommending B12 intake for the elderly.

Because the project is ongoing as indicated above, and many comments were solicited and have been received on the first report in the series (Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride), it has been possible to introduce refinements in introductory material (Chapters 1 through 3) and in the discussion of uses of DRIs (Chapter 13 in this report). For example, it is now clearly stated that a detrimental nutrient-nutrient interaction could be used as the critical adverse effect in setting a UL for a nutrient. Among the comments have been requests for additional guidance in the practical application of DRIs. The newly formed Subcommittee on the Interpretation and Uses of Dietary Reference Intakes will work toward that end.

This report reflects the work of the Food and Nutrition Board's DRI Committee; the expert Panel on Folate, Other B Vitamins, and Choline; and the UL Subcommittee. The support of the government of Canada and Canadian scientists in this initiative represents a pioneering first step in the standardization of nutrient reference intakes at least within one continent. A brief description of the overall project of the DRI Committee and of the panel's task are given in Appendix A. It is hoped that the critical, comprehensive analyses of available information and of knowledge gaps in this initial series of reports will greatly assist the private sector, foundations, universities, government laboratories, and other institutions with their research interests and with the development of a productive research agenda for the next decade.

The DRI Committee; the Panel on Folate, Other B Vitamins, and Choline; and the UL Subcommittee wish to extend sincere thanks to the many experts who have assisted with this report by giving presentations, providing written materials, participating in discussions, analyzing data, and other means. Many, but far from all, of these people are named in Appendix B. Special thanks go to Robert A. Jacob and Donald M. Mock, who made major contributions to chapters on niacin and biotin, respectively, and to staff at the National Center for Health Statistics, the Food Surveys Research Group of the Agricultural Research Service, and the Department of Statistics at Iowa State University for extensive analyses of survey data.

The respective chairs and members of the panel and subcommittee have performed their work under great time pressure. Their dedication made the completion of this report possible. All gave of their time willingly and without financial reward; both the science and practice of nutrition are major beneficiaries.

This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council's Report Review Committee. The purpose of this independent review is to provide candid and critical comments to assist the authors and the IOM in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The content of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their participation in the review of this report: Frederick C. Battaglia, M.D., University of Colorado Health Sciences Center; Enriqueta C. Bond, Ph.D., Burroughs Wellcome Fund; Patricia K. Crumrine, M.D., Children's Hospital; Krishnamurti Dakshinamurti, Ph.D., University of Manitoba; Gary Flamm, Ph.D., Flamm Associates; Theresa Glanville, Ph.D., Mount Saint Vincent University; John Hathcock, Ph.D., Council for Responsible Nutrition; James Marshall, Ph.D., Arizona Cancer Center; Deborah O'Connor, Ph.D., Ross Laboratories; Claire Regan, M.S., R.D., Grocery Manufacturers of America; Eric Rimm, Sc.D., Harvard School of Public Health; Killian Robinson, M.D., Cleveland Clinic Foundation; Robert Rucker, Ph.D., University of California-Davis; Robert F. Schilling, M.D., University of Wisconsin; John Scott, Ph.D., Sc.D., M.A., University of Dublin, Trinity College.

Although the individuals listed above have provided many constructive comments and suggestions, responsibility for the final content of this report rests solely with the authoring committee and the IOM.

The DRI Committee wishes to acknowledge, in particular, the commitment shown by Roy Pitkin, chair of the panel, who steered this difficult project through what at times seemed to some of us like dangerous and uncharted waters. His ability to keep the effort and our various biases moving in a positive direction is very much appreciated.

Special thanks go to the staff of the Food and Nutrition Board and foremost to Carol Suitor, who was the study director for the panel and without whose assistance, both intellectual and managerial, this report would neither have been as polished nor as timely in its initial release. She now moves on to enjoy the peace of her new home in beautiful Vermont and we wish her well. It is, of course those at the Food and Nutrition Board who get the real work completed and so the committee wishes to thank Allison Yates, Director of the Food and Nutrition Board, for constant assistance and it also recognizes, with appreciation, the contributions of Sandra Schlicker, Elisabeth Reese, Kimberly Brewer, Alice Kulik, Sheila Moats, Gail Spears, Diane Johnson, Michele Ramsey, and Geraldine Kennedo. We also thank Judith Grumstrup-Scott and Judith Dickson for editing the manuscript and Mike Edington and Claudia Carl for assistance with publication.

Vernon Young

Chair, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes

Cutberto Garza

Chair, Food and Nutrition Board

Copyright © 1998, National Academy of Sciences.
Bookshelf ID: NBK114325
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