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News from the National Academies
Date: April 7, 1998
Contacts: Dan Quinn, Media Relations Officer
Sean McLaughlin, Media Relations Assistant
(202) 334-2138; e-mail <news@nas.edu>

EMBARGOED: NOT FOR PUBLIC RELEASE BEFORE NOON EDT TUESDAY, APRIL 7


Adults Need to Increase Intake of Folate;
Some Women Should Take More


WASHINGTON -- Women who might become pregnant need 400 micrograms of folic acid per day to reduce their risk of having a child with neural tube defects, according to the latest report on Dietary Reference Intakes (DRIs) from the Institute of Medicine. The report--the second in a new series by American and Canadian scientists--provides Recommended Dietary Allowances (RDAs) and other dietary reference values for B vitamins, of which folate is one, and choline. It says that all adult men and women need 400 micrograms of folate in their diet--a level that many in the United States have not met, according to surveys completed before January of this year, when many foods began to be fortified with folic acid, a synthetic form of folate. But it emphasized the special needs of childbearing women.


"Research over the past decade strongly indicates that women capable of becoming pregnant should eat a varied diet and also take extra folic acid, especially in the month just prior to conception and the first month of pregnancy," said committee chair Roy M. Pitkin, professor emeritus of obstetrics and gynecology at University of California, Los Angeles. "They can best get folic acid from fortified cereal grains or from a supplement."


Since fortification of enriched cereal grains began, folic acid can be found in enriched bread, pasta, flour, crackers, breakfast cereal, rice, and many other foods in the United States. To reduce the risk of neural tube defects, women capable of becoming pregnant should consume 400 micrograms of folic acid daily from fortified foods, vitamin supplements, or a combination of the two, the report says. This is in addition to the naturally occurring folate they obtain from a varied diet. Whether these women can rely totally on the folate in food is uncertain, since research has involved giving only additional amounts of folic acid.


Neural tube defects such as spina bifida result from a disruption during the development of the fetus's central nervous system in the first month of pregnancy, when most women do not realize they are pregnant. A common type of congenital malformation of the central nervous system, neural tube defects may appear as incomplete closure of the spinal column or even the absence of part of the brain. In the United States and Canada they occur in about one birth per 1,000.


The report also says that although most Americans and Canadians get sufficient vitamin B12 in their food, between 10 percent and 30 percent of older adults have lost the ability to adequately absorb the naturally occurring form of B12 found in food. People over age 50 should meet most of their recommended intake with synthetic B12 from fortified foods or vitamin supplements.


New Dietary Standards


The committee's report on Dietary Reference Intakes expands on the Recommended Dietary Allowances set periodically by the National Academy of Sciences since 1941. Five additional reports on antioxidants, trace elements, electrolytes and water, macronutrients, and other food components will follow. Dietary Reference Intakes contain four categories of recommendations, including some values intended to help individuals optimize their health and some to help them avoid consuming too much of a nutrient.


In addition to folate, the report recommends individual intakes for thiamin, riboflavin, niacin, vitamins B6 and B12, pantothenic acid, biotin, and choline. Where possible, it also specifies intake levels above which health problems might occur. Except for folate, recommended intakes for these vitamins have not changed substantially since the last group of recommendations was published in the United States in 1989 and in Canada in 1990. Most Americans and Canadians already meet their requirements for these vitamins through their diet.


A great deal of research in the past two decades has centered on the roles that B vitamins may play in reducing the risk of cardiovascular disease, cancers, or various psychiatric or mental disorders. Although such research is provocative and promising, it is not yet solid enough to serve as the basis for setting recommendations for nutrient intake, the report says. Therefore, rather than set recommended intake levels to reduce the risk of these diseases, the committee based its recommended intake levels on values shown to guard against anemia or other conditions that can develop when these vitamins are lacking.


Research has shown that consumption of folate and vitamin B6 can reduce elevated levels of homocysteine in the blood, and some studies have linked lower homocysteine concentrations with a decreased risk of cardiovascular disease. But there is conflicting evidence about whether increasing folate or B6 intake leads directly to a lower incidence of vascular and heart disease. Likewise, data showing that increased folate may protect against colorectal cancer do not provide conclusive evidence of a benefit, the report says.


Upper Levels Set


The committee set the tolerable upper intake level for vitamin B6 at 100 milligrams per day for adults. Intakes above this amount could cause sensory neuropathy, a nerve disorder that can lead to pain, numbness, and weakness in the limbs. Likewise, adults with vitamin B12 deficiency who take excess folic acid place themselves at greater risk of progressive, crippling neurologic damage. For folic acid, the committee set the tolerable upper intake level for adults at 1,000 micrograms, or 1 milligram, per day.


Individuals who consume too much niacin have been shown to feel a flush, warm sensation, itching, and other symptoms. The committee set the tolerable upper intake level for niacin at 35 milligrams per day. Some individuals who take high-dose, over-the-counter niacin supplements may exceed this amount regularly. The tolerable upper level for choline was set at 3.5 grams per day for adults. Intakes above that level could cause hypotension, or low blood pressure, and a fishy body odor in some people.


Because the committee was unable to identify studies conducted on the adverse effects of taking large doses of many of the B vitamins, it did not set upper limits for thiamin, riboflavin, vitamin B12, pantothenic acid, and biotin. Due to the lack of data, the committee urged extra caution with regard to excessive consumption of these vitamins.


A list of committee, panel, and subcommittee members follows. The Institute of Medicine is a private, non-profit organization that provides health policy advice under a congressional charter granted to the National Academy of Sciences. This study was funded by the U.S. Department of Health and Human Services, the National Institutes of Health, the Centers for Disease Control and Prevention, Health Canada, the Institute of Medicine, and the Dietary Reference Intakes Corporate Donors Fund. Contributors to the fund include Roche Vitamins Inc., Mead Johnson Nutrition Group, Daiichi Fine Chemicals Inc., Kemin Foods Inc., M&M Mars, Weider Nutrition Group, and Natural Source Vitamin E Association.


Read the full text of Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Cholinefor free on the Web, as well as more than 1,800 other publications from the National Academies. Printed copies are available for purchase from the National Academy Press Web siteor at the mailing address in the letterhead; tel. (202) 334-3313 or 1-800-624-6242. Reporters may obtain a pre-publication copy from the Office of News and Public Information at the letterhead address (contacts listed above).


      INSTITUTE OF MEDICINE
      Food and Nutrition Board

      PANEL ON FOLATE AND OTHER B VITAMINS

      ROY M. PITKIN, M.D.(1) (CHAIR)
      Department of Obstetrics and Gynecology
      University of California, School of Medicine
      Los Angeles

      LINDSAY H. ALLEN, PH.D., R.D.
      Program in International Nutrition
      Department of Nutrition
      University of California
      Davis

      LYNN B. BAILEY, PH.D.
      Food Science and Human Nutrition Department
      University of Florida
      Gainesville

      MERTON BERNFIELD, M.D.(1)
      Joint Program in Neonatology
      Department of Pediatrics
      Harvard Medical School
      Boston

      PHILIPPE DE WALS, M.D., PH.D.
      School of Public Health
      University of North Carolina
      Chapel Hill

      RALPH GREEN, M.D.
      Department of Pathology
      University of California at Davis Medical Center
      Sacramento

      DONALD B. MCCORMICK, PH.D.
      Department of Biochemistry
      Rollins Research Center
      Emory University School of Medicine
      Atlanta

      ROBERT M. RUSSELL, M.D.
      Jean Mayer USDA Human Nutrition Research Center on Aging
      Tufts University
      Boston

      BARRY SHANE, PH.D.
      Department of Nutritional Sciences
      University of California
      Berkeley

      STEVEN ZEISEL, M.D., PH.D.
      Department of Nutrition
      University of North Carolina School of Public Health
      Chapel Hill

      STANDING COMMITTEE ON THE SCIENTIFIC EVALUATION OF DIETARY REFERENCE INTAKES

      VERNON R. YOUNG, PH.D., D.SC.(1,2) (CHAIR)
      Laboratory of Human Nutrition
      Massachusetts Institute of Technology
      Cambridge

      JOHN W. ERDMAN JR., PH.D. (CO-VICE CHAIR)
      Division of Nutritional Sciences
      College of Agriculture
      University of Illinois
      Urbana-Champaign

      JANET C. KING, PH.D.(1) (CO-VICE CHAIR)
      University of California, Berkeley, and
      USDA Western Human Nutrition Research Center
      Presidio of San Francisco

      LINDSAY H. ALLEN, PH.D.
      Department of Nutrition
      University of California
      Davis

      STEPHANIE A. ATKINSON, PH.D.
      Department of Pediatrics
      Faculty of Health Sciences
      McMaster University
      Hamilton, Canada

      JOHANNA T. DWYER, D.SC., R.D.
      Departments of Medicine and of Community Health
      Tufts Medical School and School of Nutrition Science and Policy
      Boston

      JOHN D. FERNSTROM, PH.D.
      University of Pittsburgh School of Medicine, and
      Western Psychiatric Institute and Clinic
      Pittsburgh

      SCOTT M. GRUNDY, M.D., PH.D.(1)
      Center for Human Nutrition
      University of Texas, Southwestern Medical Center
      Dallas

      CHARLES H. HENNEKENS, M.D., D.P.H.
      Division of Preventive Medicine
      Harvard Medical School
      Boston

      SANFORD A. MILLER, PH.D.
      Graduate School of Biomedical Sciences
      University of Texas Health Science Center
      San Antonio

      SUBCOMMITTEE ON UPPER REFERENCE LEVELS OF NUTRIENTS

      IAN CRAIG MUNRO, PH.D. (CHAIR)
      CanTox Inc.
      Mississauga, Ontario
      Canada

      WALTER MERTZ, M.D.
      USDA Human Nutrition Research Center (retired)
      Rockville, Md.

      RITA B. MESSING, PH.D.
      Division of Environmental Health
      Minnesota Department of Health
      St. Paul

      SANFORD A. MILLER, PH.D.
      Graduate School of Biomedical Sciences
      University of Texas Health Science Center
      San Antonio

      SUZANNE P. MURPHY, PH.D., R.D.
      Department of Nutritional Sciences
      University of California
      Berkeley

      JOSEPH V. RODRICKS, PH.D.
      ENVIRON Corp.
      Arlington, Va.

      IRWIN H. ROSENBERG, M.D.(1)
      Clinical Nutrition Division
      Tufts University, and
      New England Medical Center
      Boston

      STEPHEN L. TAYLOR, PH.D.
      Department of Food Science and Technology
      Food Processing Center
      University of Nebraska
      Lincoln

      ROBERT H. WASSERMAN(2)
      Department of Physiology
      New York State College of Veterinary Medicine
      Cornell University
      Ithaca

      INSTITUTE OF MEDICINE STAFF

      ALLISON A. YATES
      Director, Food and Nutrition Board

      CAROL W. SUITOR
      Study Director

      SANDRA SCHLICKER
      Senior Program Officer

      ________________________________________

      1 Member, Institute of Medicine
      2 Member, National Academy of Sciences