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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.
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.
Show detailsTABLE E-1Methodological Problems with Laboratory Values for B Vitamins
| Thiamin | Riboflavin | Niacin | B6 | Folate | B12 | Pantothenic Acid | Biotin | Choline | |
|---|---|---|---|---|---|---|---|---|---|
| Are precise, accurate methods available? | Yes | Yes | Yes | Yes | Needs improvement | Yes | Needs improvement | Being improved | Yes |
| What is known about the analytic sensitivity and specificity of the methods? | Good | Good | Good | Good | Good, but incomplete assays for all forms | Fair; some metabolite interference noted | Needs improvement | Variable | Mass spectrometry specific to 5 pmol |
| Is there good agreement in results from use of different methods? | Yes | Yes | Yes | Yes, for most | No, see Gunter et al., 1996a | No, e.g., Euglena gracilis gives lower values than does Lactobacillis leichmannii | Fair, limited | No | Yes |
| Is there good agreement in results if different laboratories use the same methods? | Yes | Yes | Yes | Fair | No, see Gunter et al., 1996a | No, nonisotopic and radioassays do not agree closely | Fair | Fair, limited | Yes |
| 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 methods | Generally lower now | No change | |||
| How are problems with methods addressed in the report? | Not necessary | Earlier under- and over-estimations of flavins noted. | Questions for research | Not necessary | Detailed subsections, questions for research | Need for internal reference is stated and values given when available; questions for research. | Questions for research | Short subsection | Not 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
| Thiamin | Riboflavin | Niacin | B6 | Folate | B12 | Pantothenic Acid | Biotin | Choline | |
|---|---|---|---|---|---|---|---|---|---|
| Are precise, accurate methods available?a | Substantial, acceptable quality | Substantial, acceptable quality | Substantial, acceptable quality | Substantial, acceptable quality | Conflicting, variable quality | Conflicting, quality mootb | Conflicting | Lacking, being improved | Substantial, acceptable quality |
| Is there good agreement in results using different methods? | Fair when allowance is made for specificity differences | No, see Gregory (1997), Martin et al. (1992), Pfeiffer et al. (1997), Tamura et al. (1997)c | No, tissue methods poorly developed | — | Insufficient comparisons to assess | Yes, but very limited experience | |||
| Over time, how have changes in methods affected estimates? | None noted | About the same or slightly lower | None noted | Slightly higher now | New methods give somewhat higher results for some foods | — | — | — | Old 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.
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