Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998) / Chapter Skim
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2 The B Vitamins and Choline: Overview and Methods
2 The B Vitamins and Choline: Overview and Methods
Pages 27-40
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From page 27... ...
Methocis OVERVIEW This report focuses on the eight B complex vitamins thiamin, riboflavin, niacin, vitamin B6, folate, vitamin Bit, pantothenic acid, and biotin and choline. These water-soluble nutrients fall into two categories: those involved in the reactions of intermediary metabolism relate ci to energy procluc tion and re Fox status an ci tho se involveci in the transfer of single-carbon units.
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Results from animal experiments are generally not applicable to nutritional deficiencies, chronic diseases, and toxic effects in humans, but selected animal studies are consiclereci in the absence of human ciata. The strategies used for identifying potentially relevant studies are summarized in Appendix D
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Statistical association floes not imply causation, and this is especially true for relationships between nutrient intake and clevelopmental abnormalities or chronic disease risk reduction as well as for toxic effects. The criteria proposed by Hill (1971)
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Ages O through 6 Months To derive the AI value for infants ages 0 through 6 months, the mean intake of a nutrient was calculated baseci on ~ 1 ~ the average concentration of the nutrient from 2 to 6 months of lactation using consensus values from several reported studies, if possible, and (2) an average volume of milk intake of 780 mL/ciay.
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extrapolation upward from the AI for infants ages 0 through 6 months by using the metabolic weight ratio and (2) extrapolation downward from the EAR for Young adults bY ad, c, , justing for metabolic body size and growth and adding a factor for variability or from the AI if the recommended intake for adults was an AI.
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Setting the RDA To account for variability in requirements because of growth rates and other factors, a 10 percent coefficient of variation (CV) for the TABLE 2-1 Growth Factors Used to Extrapolate DRIs Age Group Growth Factor 7 mo-3 y 4-8 y 9-13 y 14-18 y, Males 14-18 y, Females 0.30 0.15 0.15 0.15 0.00 NOTE: Growth beyond age 13 for females is assumed to represent a negligible increased requirement for vitamins.
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For choline, the AI is based on the increase in maternal weight. Methods to Determine Increased Needs for Lactation For the B vitamins and choline, it is assumed that the total requirement of lactating women equals the requirement for the nonpregnant, nonlactating woman of similar age plus an increment to cover the amount of the nutrient neecleci for milk production.
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The use of creatinine corrections to allow for assay of random fasting urine samples rather than 24-hour collections may neeci to include considerations of differences in creatinine excretion by age. · Depletion-repletion studies assess requirements by identifying intakes that return status indicators to the prestucly baseline values.
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Therefore, the values reported by nationwide surveys or studies that rely on self-report may be somewhat inaccurate and possibly biased. Food composition databases that are used to calculate nutrient in take from self-rep orte ci and observe ci in take ciata in tro cluce e rrors clue to random variability, genetic variation in the nutrient content, analytical errors, and missing or imputed ciata.
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The 1994 to 1995 CSFII collected two nonconsecutive 24-hour recalls from approximately 5,600 subjects of all ages. Both surveys used the food composition database developed by USDA to calculate nutrient intakes (Perloff et al., 1990~.
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Sources of Data on Supplement Intake Although subjects in the CSFII were askoci about the use of clietary supplements, quantitative information was not collected. Data on supplement intake obtained from NHANES III were reported as a part of total nutrient intake (Appenclix H)
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Data from the 1995 CSFII were used to iclentify major contributors. In contrast, the food sources listed are those with the high concentrations of the nutrient; no consideration is given to the amount consumed.
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1993. Methodological issues in the measurement of cardiovascular risk factors: Within-person variability in selected serum lipid measures results from the Third National Health and Nutrition Survey (NHANES III)
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1996. A semiparametric transformation approach to estimating usual daily intake distributions.
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