subjects with serum B₁₂ less than 150 pmol/L (200 pg/mL) had an elevated MMA concentration.

Studies of B₁₂ intake and serum B₁₂ concentration provide very limited information on the relationship of the two. In Finland, vegans consuming an uncooked (“living food”) diet were estimated to consume a mean of 1.8 µg/day of B₁₂ (range 0 to 12.8 µg) (Rauma et al., 1995), but the accuracy of the dietary intake data is uncertain. The 16 vegans who ate seaweed (the main source of B₁₂ reported) had B₁₂ concentrations twice as high as those not eating seaweed (mean of 220 pmol/L [300 pg/mL] compared with 105 pmol/L [142 pg/mL]). On this diet 57 percent of the vegans had serum B₁₂ concentrations less than 200 pmol/L (270 pg/mL). A study by Draper and colleagues (1993) provided dietary data on vegans that were not sufficient for drawing conclusions about diet-B₁₂ relationships. Neither Garry and coworkers (1984) nor Sahyoun and colleagues (1988) separated data with regard to supplement use, so their data are not interpretable for setting EARs. A study of a macrobiotic population (Miller et al., 1991) revealed that more than half of the adults had low serum B₁₂ concentrations and nearly onethird were excreting high amounts of MMA, but dietary information from the study was not sufficient for drawing conclusions. Moreover, studies need to be conducted in younger persons in whom B₁₂ absorption is more likely to be normal.

On the basis of hematological evidence and serum B₁₂ values, the EAR for B₁₂ is estimated to be 2 µg/day for men and women ages 19 through 50 years. Sufficient data were not available to enable differences in requirements to be discerned for men and women in these age groups.

The RDA for B₁₂ is set by assuming a coefficient of variation (CV) of 10 percent (see Chapter 1) because information is not available on the standard deviation of the requirement for B₁₂; the RDA is defined as equal to the EAR plus twice the CV to cover the needs of