Am J Clin Nutr. 1990 Dec; 52(6): 1073-6.

Vitamin B-12: low milk concentrations are related to low serum concentrations in vegetarian women and to methylmalonic aciduria in their infants.

Specker BL, Black A, Allen L, Morrow F.

Department of Pediatrics, University of Cincinnati Medical Center, OH 45267-0541.

In a group of 13 strict vegetarian and 6 omnivorous lactating women, relationships were studied among maternal milk and serum vitamin B-12, and milk vitamin B-12 and infant urinary methylmalonic acid (MMA) excretion. Milk vitamin B-12 concentrations were lower in women consuming a strict vegetarian diet compared with an omnivorous diet. Milk vitamin B-12 was inversely related to length of time on a vegetarian diet and positively correlated with maternal serum vitamin B-12 concentrations. Infant urinary MMA excretion was inversely related to milk vitamin B-12 concentrations less than 362 pmol/L. The 1989 recommended dietary allowance for vitamin B-12 of 221 pmol/d for infants is close to the intake below which infant urinary MMA excretion is increased. We conclude that the current RDA for infants provides little margin of safety.