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Dietary Reference Intakes Research Synthesis Workshop Summary (2007) / Chapter Skim
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4 Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline
Pages 35-48

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From page 35...
... DISCUSSION OF RESEARCH RECOMMENDATIONS: THIAMIN, RIBOFLAVIN, NIACIN, PANTOTHENIC ACID, AND CHOLINE Presenter: Steven H Zeisel This presentation highlighted major new developments, pointed out that genetic polymorphism and epigenetics merit special attention, and addressed major research gaps and the progress made.
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From page 36...
... Such genetic polymorphisms are not rare. In setting Recommended Dietary Allowances (RDAs)
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From page 37...
... improvement of nutrient databases to differentiate the forms of niacin -- specifically the naturally occurring niacin content of foods and niacin added as a fortificant. Progress made Some progress has been made in addressing niacin research gaps since 1998: • A toxicology panel was convened; in 2005, it reported on the toxicity and potential toxicity of higher dose niacin (Cosmetic Ingredient Review Expert Panel, 2005)
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From page 38...
... With regard to the DRIs, both of those trials probably are most useful for defining human exposure and potential toxicity at high doses. However, they might also be useful in defining peripheral vascular disease function as an end point for niacin optimization.
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From page 39...
... . Potential functional markers for choline include muscle damage, lymphocyte apoptosis, and elevated homocysteine after a methionine load.
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From page 40...
... Further investigation revealed that individuals who develop organ dysfunction when deprived of choline have a greatly increased risk if they have one or two of several genetic polymorphisms in genes of choline or folate metabolism. The study found a polymorphism in phosphatidylethanolamine-N-methyltransferase (PEMT)
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From page 41...
... reported that the risk for cleft lip and palate in the high choline intake group is half that of the low choline intake group. A large epidemiologic study reported an inverse relationship between dietary choline intake and plasma total homocysteine concentration (Cho et al., 2006)
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From page 42...
... Vitamin B6 Major research gaps listed for vitamin B6 (pyridoxine) include better indicators for the requirement and information about genetic variation, chronic disease prevention, interaction with other vitamins, and the needs of children, the elderly, and pregnant and lactating women.
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From page 43...
... Zeisel in relation to choline deficiency. Although these two human polymorphisms in folate metabolism are associated with increased risk for neural tube defects and alter one-carbon metabolism, they make up only a small fraction of the total genetic component that poses risk for neural tube defects.
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From page 44...
... Little progress has been made in determining whether folate requirements vary by trimester in pregnancy or in obtaining data specific to folate requirements for children, elderly persons, and women of reproductive age. Interactions with other nutrients Considerable data are available now regarding interactions of folate with certain other B vitamins and choline, both of which affect methylation status -- especially the methylation of DNA and histones, which has effects on gene expression and stem cell programming.
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From page 45...
... showed reduced natural killer cell cytotoxicity in women with folic acid present in the plasma. Vitamin B12 Major gaps related to vitamin B12 included • its role in vascular disease; • the impact of genetic variation; • requirements in the elderly (one in six individuals over the age of 65 years is believed to be at risk for deficiency of vi tamin B12 )
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From page 46...
... fetal/stem cell programming. Disease and Pathology Outcomes MTHFR polymorphism inhibits the remethylation cycle, which may increase the homocysteine concentration of the blood, decrease methylation potential, and alter chromatin structure and gene expression.
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From page 47...
... Fetal and Stem Cell Programming Dr. Stover emphasized the importance of investigating fetal and stem cell programming, which first received attention by the nutrition community related to Barker's fetal origins of adult disease hypothesis.
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From page 48...
... Concluding Remarks In conclusion, Dr. Stover emphasized the need to consider genetic variation, determine relevant parameters, and determine whether or not individual recommendations for B vitamin requirements are needed.
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Key Terms

  • research gaps
  • folic acid
  • pantothenic acid
  • genetic variation
  • homocysteine concentration

  • neural tube
  • choline intake
  • tube defects
  • genetic polymorphisms
  • mthfr polymorphism

  • cell programming
  • stem cell
  • dietary choline
  • genetic polymorphism
  • serum folate

  • genetic variants
  • low choline
  • folate requirements
  • choline content
  • folate requirement

  • folate metabolism
  • choline deficiency
  • folate concentration
  • filling research
  • human exposure

  • gaps particular
  • cardiovascular disease
  • vascular disease
  • chronic disease
  • increased risk


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