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). |
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|
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. |
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