Response of vitamin B12 status to a controlled B12 intake in nonpregnant, pregnant, and lactating women

Abstract

As part of a 12‐wk controlled feeding study, pregnant (n=26, 27 wk gestation), lactating (n=28, 5 wk postpartum), and nonpregnant (n=21) women consumed the study vitamin B12 dose of 7.5 μg/d [prenatal supplement (2.6 μg/d) and natural food (~4.9 μg/d)]. All participants achieved adequate vitamin B12 status throughout the study. Serum total vitamin B12 remained constant in pregnant and lactating women, whereas it increased in nonpregnant women (P=0.001). At study end, total B12 (mean ± SD) was lower in pregnant women (335 ± 104 pmol/L) than lactating (496 ± 127 pmol/L, P<0.001) and nonpregnant (422 ± 82 pmol/L, P=0.015) women. The consumption of the study B12 dose increased both serum holotranscobalamin (holoTC) and the fraction of total serum vitamin B12 bound to TC (holoTC/B12 ratio) within physiologic groups (P ≤0.001 and P ≤0.037, respectively). At study end, pregnant women had higher holoTC/B12 ratio (31%) than nonpregnant women (22%, P=0.035) and lactating women (24%, P=0.056) suggesting that pregnancy increased the tissue availability of circulating B12. Overall, these data suggest that consumption of the study vitamin B12 dose (~ 2.5 times the RDA) met the vitamin B12 requirements of our study participants and maintained B12 concentrations in third trimester pregnant women by increasing holoTC concentrations. Funded in part by USDA, AEB‐ENC and the Beef Checkoff.