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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

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Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
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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)

Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×

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

Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×

 

Thiamin

Riboflavin

Niacin

B6

How are problems with methods addressed in the report?

Not necessary

Earlier under-and over-estimations of flavins noted.

Questions for research

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-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).

Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×

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.

Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×
Page 456
Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×
Page 457
Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×
Page 458
Suggested Citation:"E Methodological Problems Associated with Laboratory Values and Food Composition Data for B Vitamins." Institute of Medicine. 1998. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press. doi: 10.17226/6015.
×
Page 459
Next: F Dietary Intake Data from the Boston Nutritional Status Survey, 1981–1984 »
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline Get This Book
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Since 1941, Recommended Dietary Allowances (RDAs) has been recognized as the most authoritative source of information on nutrient levels for healthy people. Since publication of the 10th edition in 1989, there has been rising awareness of the impact of nutrition on chronic disease. In light of new research findings and a growing public focus on nutrition and health, the expert panel responsible for formulation RDAs reviewed and expanded its approach--the result: Dietary Reference Intakes.

This new series of references greatly extends the scope and application of previous nutrient guidelines. For each nutrient the book presents what is known about how the nutrient functions in the human body, what the best method is to determine its requirements, which factors (caffeine or exercise, for example) may affect how it works, and how the nutrient may be related to chronic disease.

This volume of the series presents information about thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline.

Based on analysis of nutrient metabolism in humans and data on intakes in the U.S. population, the committee recommends intakes for each age group--from the first days of life through childhood, sexual maturity, midlife, and the later years. Recommendations for pregnancy and lactation also are made, and the book identifies when intake of a nutrient may be too much. Representing a new paradigm for the nutrition community, Dietary Reference Intakes encompasses:

  • Estimated Average Requirements (EARs). These are used to set Recommended Dietary Allowances.
  • Recommended Dietary Allowances (RDAs). Intakes that meet the RDA are likely to meet the nutrient requirement of nearly all individuals in a life-stage and gender group.
  • Adequate Intakes (AIs). These are used instead of RDAs when an EAR cannot be calculated. Both the RDA and the AI may be used as goals for individual intake.
  • Tolerable Upper Intake Levels (ULs). Intakes below the UL are unlikely to pose risks of adverse health effects in healthy people.

This new framework encompasses both essential nutrients and other food components thought to pay a role in health, such as dietary fiber. It incorporates functional endpoints and examines the relationship between dose and response in determining adequacy and the hazards of excess intake for each nutrient.

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