Folate supplementation during lactation: maternal folate status, human milk folate content, and their relationship to infant folate status.

The influence of maternal folate status and human milk folate content on infant folate status was studied in 11 lactating women taking folate supplements throughout pregnancy and lactation. Nursing mothers not taking folate supplements, as well as nonpregnant, nonlactating women, were also studied. Maternal and infant serum and red blood cell (RBC) folate concentrations, as well as the "free" and total folate contents of human milk samples, were determined at 6 and 12 weeks post partum. Mothers taking folate supplements maintained blood folate concentrations higher than those of unsupplemented mothers and similar to or higher than those of normal adults. Infants of both supplemented and unsupplemented mothers maintained similar blood folate levels. Positive correlations were found between maternal RBC folate concentrations and infant RBC folate concentrations at 6 weeks (r = 0.62) and 3 months (r = 0.74), but no relationship was found between maternal folate status and human milk folate activity. Human milk folate levels increased with the progression of lactation, were higher in the evening than earlier in the day, and were higher at the end of a feeding than at the beginning. These results indicate that human milk folate levels are maintained at the expense of maternal reserves and that folate supplementation during lactation may be of value for preservation of maternal reserves.