Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline

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Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998)
Institute of Medicine (IOM)

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. "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 B₁₂ Intake Considered in Setting the Estimated Average Requirement for B₁₂ for Adults

Reference	Description	Dietary B₁₂ Intake
Suggested dietary B₁₂ 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 B₁₂ values below the 2.5 percentile (< 120 pmol/L [162 pg/mL]) not caused by disease or vegetarianism	1.5 ± 0.4 (SD^c) µg/d of B₁₂ (range 0.6–1.9)
Suggested dietary B12 average requirement > 1.0 µg/d
Winawer et al., 1967	1 64-y-old vegan with B₁₂-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 B₁₂ from milk, assuming that it was not boiled
Baker and Mathan, 1981	4 East Indians with B₁₂ deficiency anemia secondary to diet	NA^d
^a p.o. = by mouth. ^b Based on USDA data (URL http://www.nal.usda.gov/fnic/foodcomp/).

appear to be impaired, the combination of stores and absorbed crystalline B₁₂ 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 B₁₂ deficiency after a total gastrectomy; for example, megaloblastic anemia has been typically diagnosed 2 to 5 years after a total gastrectomy (Chanarin, 1990).