. "9 Vitamin B12."
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: The National Academies Press, 1998.
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DRI Dietary Reference Intakes: For Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline
TABLE 9-7 Studies of Individuals with Low Vitamin B 12 Intake Considered in Setting the Estimated Average Requirement for B 12 for Adults
Suggested dietary B 12 average requirement > 1.5 µg/d
Stewart et al., 1970
1 Hindu woman with megaloblastic anemia
0.5 µg/d (analyzed homogenate)
Narayanan et al., 1991
10 subjects with serum B
12 values below the 2.5 percentile (< 120 pmol/L [162 pg/mL]) not caused by disease or vegetarianism
1.5 ± 0.4 (SD
) µg/d of B c 12 (range 0.6–1.9)
Suggested dietary B12 average requirement > 1.0 µg/d
Winawer et al., 1967
1 64-y-old vegan with B
12-deficient megaloblastic anemia, gastritis on biopsy, and normal gastric acidity
Assumed to be negligible
Jathar et al., 1975
7 East Indian lactovegetarians
0.3–0.8 µg/d of B
12 from milk, assuming that it was not boiled
Baker and Mathan, 1981
4 East Indians with B
12 deficiency anemia secondary to diet
p.o. = by mouth. a
Based on USDA data (URL b http://www.nal.usda.gov/fnic/foodcomp/).
appear to be impaired, the combination of stores and absorbed crystalline B
12 may cover needs for an extended period.
The estimates above for the period of protection afforded by body stores are consistent with the periods required to develop overt signs of B
12 deficiency after a total gastrectomy; for example, megaloblastic anemia has been typically diagnosed 2 to 5 years after a total gastrectomy (Chanarin, 1990).