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97 to 98 percent of the individuals in the group (therefore, for B12 the RDA is 120 percent of the EAR).

RDA for Children

1–3 years

0.9 µg/day of vitamin B12

 

4–8 years

1.2 µg/day of vitamin B12

RDA for Boys

9–13 years

1.8 µg/day of vitamin B12

 

14–18 years

2.4 µg/day of vitamin B12

RDA for Girls

9–13 years

1.8 µg/day of vitamin B12

 

14–18 years

2.4 µg/day of vitamin B12

Adults Ages 19 through 50 Years

Method Used to Estimate the Average Requirement

No single indicator was judged to be a sufficient basis for deriving an EAR for adults. It was not deemed appropriate to base the EAR on an examination limited to studies that provided data on mean cell volume (MCV) or serum B12 or any other single laboratory value. Data on men and women were examined together because of small numbers. Three general approaches were considered to derive the EAR for adults: determination of the amount of B12 needed to maintain adequate hematological status (as measured by stable hemoglobin value, normal MCV, and normal reticulocyte response) and serum B12 values in persons with pernicious anemia or with known intakes that were very low in dietary B12; use of daily B12 turnover to estimate the amount of B12 needed to maintain body stores at a specified level; and estimation of the dietary B12 intake by healthy adults that corresponds to adequate serum values of B12 and of MMA.

The first approach was chosen as the primary method for deriving an EAR because it is the only approach for which there are sufficient and reliable data for estimating need. A low serum B12 value in persons with pernicious anemia was assumed to indicate incomplete response to treatment.

Primary Criterion: Maintenance of Hematological Status and Serum B12Values. The primary method used to derive the EAR for adults estimates the amount of B12 needed for the maintenance of hematological status and serum B12 values, primarily by using data derived from patients with pernicious anemia in remission. Data from studies of vegetarians were also examined to determine whether they



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