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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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EMethodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins

TABLE E-1Methodological Problems with Laboratory Values for B Vitamins

ThiaminRiboflavinNiacinB6FolateB12Pantothenic AcidBiotinCholine
Are precise, accurate methods available?YesYesYesYesNeeds improvementYesNeeds improvementBeing improvedYes
What is known about the analytic sensitivity and specificity of the methods?GoodGoodGoodGoodGood, but incomplete assays for all formsFair; some metabolite interference notedNeeds improvementVariableMass spectrometry specific to 5 pmol
Is there good agreement in results from use of different methods?YesYesYesYes, for mostNo, see Gunter et al., 1996aNo, e.g., Euglena gracilis gives lower values than does Lactobacillis leichmanniiFair, limitedNoYes
Is there good agreement in results if different laboratories use the same methods?YesYesYesFairNo, see Gunter et al., 1996aNo, nonisotopic and radioassays do not agree closelyFairFair, limitedYes
Over time, how have changes in methods affected estimates?Generally lower because of more specific chromatographic separation (especially high-performance liquid chromatography)Trends vary depending on method.Radioassays were unreliable before 1978. Recent introduction of nonisotopic assays has led to higher results.Little change in methodsGenerally lower nowNo change
How are problems with methods addressed in the report?Not necessaryEarlier under- and over-estimations of flavins noted.Questions for researchNot necessaryDetailed subsections, questions for researchNeed for internal reference is stated and values given when available; questions for research.Questions for researchShort subsectionNot necessary
a

Gunter EW, Bowman BA, Caudill SP, Twite DB, Adams MJ, Sampson EJ. 1996. Results of an international round robin for serum and whole-blood folate. Clin Chem 42:1689–1694.

TABLE E-2Methodologic Problems with Obtaining Food Composition Data for B Vitamins

ThiaminRiboflavinNiacinB6FolateB12Pantothenic AcidBiotinCholine
Are precise, accurate methods available?aSubstantial, acceptable qualitySubstantial, acceptable qualitySubstantial, acceptable qualitySubstantial, acceptable qualityConflicting, variable qualityConflicting, quality mootbConflictingLacking, being improvedSubstantial, acceptable quality
Is there good agreement in results using different methods?Fair when allowance is made for specificity differencesNo, see Gregory (1997), Martin et al. (1992), Pfeiffer et al. (1997), Tamura et al. (1997)cNo, tissue methods poorly developedInsufficient comparisons to assessYes, but very limited experience
Over time, how have changes in methods affected estimates?None notedAbout the same or slightly lowerNone notedSlightly higher nowNew methods give somewhat higher results for some foodsOld estimates were too high, early assay not specific
a

Ratings for the B vitamins (but not for choline) are taken from Life Sciences Research Office/Federation of American Societies for Experimental Biology. 1995. Third Report on Nutrition Monitoring in the United States. Washington, DC: U.S. Government Printing Office.

b

Quality of data was rated moot if it was considered unlikely that improved data for that food component would make a difference in the assessment of nutrition-related health status and the assignment of nutrition monitoring priority status (LSRO/FASEB, 1995).

c

Gregory JF 3rd. 1997. Bioavailability of folate. Eur J Clin Nutr 51: S54–S59; Martin DC, Francis J, Protetch J, Huff J. 1992. Time dependency of cognitive recovery with cobalamin replacement: Report of a pilot study. J Am Geriatr Soc 40:168–172; Pfeiffer CM, Rogers LM, Gregory JF 3rd. 1997. Determination of folate in cereal-grain food products using trienzyme extraction and combined affinity and reversed-phase liquid chromatography. J Agric Food Chem 45:407–413; Tamura T, Mizuno Y, Johnston KE, Jacob RA. 1997. Food folate assay with protease, α-amylase, and folate conjugase treatments. J Agric Food Chem 45:135–139.

Copyright © 1998, National Academy of Sciences.
Bookshelf ID: NBK114307

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