Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998)
Chapter: E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins
E
Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins
TABLE E-1 Methodological Problems with Laboratory Values for B Vitamins
| Thiamin | Riboflavin | Niacin | B6 |
Are precise, accurate methods available? | Yes | Yes | Yes | Yes |
What is known about the analytic sensitivity and specificity of the methods? | Good | Good | Good | Good |
Is there good agreement in results from use of different methods? | Yes | Yes | Yes | Yes, for most |
Is there good agreement in results if different laboratories use the same methods? | Yes | Yes | Yes | Fair |
Over time, how have changes in methods affected estimates? | Generally lower because of more specific chromatographic separation (especially high-performance liquid chromatography) | |||
Folate | B12 | Pantothenic Acid | Biotin | Choline |
Needs improvement | Yes | Needs improvement | Being improved | Yes |
Good, but incomplete assays for all forms | Fair; some metabolite interference noted | Needs improvement | Variable | Mass spectrometry specific to 5 pmol |
No, see Gunter et al., 1996a | No, e.g., Euglena gracilis gives lower values than does Lactobacillis leichmannii | Fair, limited | No | Yes |
No, see Gunter et al., 1996a | No, nonisotopic and radioassays do not agree closely | Fair | Fair, limited | Yes |
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 |
TABLE E-2 Methodologic Problems with Obtaining Food Composition Data for B Vitamins
| Thiamin | Riboflavin | Niacin | B6 |
Are precise, accurate methods available?a | Substantial, acceptable quality | Substantial, acceptable quality | Substantial, acceptable quality | Substantial, acceptable quality |
Is there good agreement in results using different methods? | Fair when allowance is made for specificity differences | |||
Over time, how have changes in methods affected estimates? | None noted | About the same or slightly lower | None noted | Slightly higher now |
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). | ||||
Folate | B12 | Pantothenic Acid | Biotin | Choline |
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 |
Folate | B12 | Pantothenic Acid | Biotin | Choline |
Conflicting, variable quality | Conflicting, quality mootb | Conflicting | Lacking, being improved | Substantial, acceptable quality |
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 |
New methods give somewhat higher results for some foods | — | — | — | Old estimates were too high, early assay not specific |
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. | ||||
