British Journal of Nutrition

Research Article

Evidence of unmetabolised folic acid in cord blood of newborn and serum of 4-day-old infants

Mary R. Sweeneya1a2 c1, Joseph McPartlina1, Donald G. Weira1, Sean Dalya4, Kristina Pentievaa5, Leslie Dalya2 and John M. Scotta3

a1 Department of Clinical Medicine, University of Dublin, Trinity College, Dublin, Ireland

a2 Department of Public Health Medicine and Epidemiology, University College Dublin, Earlsfort Terrace, Dublin 2, Ireland

a3 Department of Biochemistry, University of Dublin, Trinity College, Dublin, Ireland

a4 Coombe Woman's Hospital, Dublin, Ireland

a5 Northern Ireland Centre for Diet and Health, University of Ulster, Coleraine BT52 ISA, Northern Ireland


Oral folic acid above certain threshold doses results in unmetabolised folic acid in serum. This raises a number of public health safety issues, principally the potential to mask pernicious anaemia; more recently the theoretical potential for high-dose folic acid to promote cancer has been highlighted. In this paper we set out to examine the appearance of unmetabolised folic acid both in cord blood from newborn full-term and premature infants and serum from 4-d-old infants post-formula feeding. Blood was collected from the umbilical cord of eleven infants in the delivery room immediately after birth. A follow-up serum sample (n 9) was collected 4d later from infants post-formula feeding. We detected unmetabolised folic acid in cord blood from all infants at birth. In addition, unmetabolised folic acid was present in serum of seven infants post-formula feeding, six of which had increased from birth. Our results imply that infants in Ireland, which does not yet have mandatory fortification, could potentially have circulatory unmetabolised folic acid at the time of birth. We do not know if the presence of folic acid in cord blood will have any adverse consequences. However, if theoretical safety concerns are borne out by future research, the likelihood is that the longer the exposure the more likely the potential for harm. This would also be the case in infants exposed to unmetabolised folic acid as a result of formula feeding.

(Received April 18 2005)

(Revised June 05 2005)

(Accepted July 07 2005)


c1 *Corresponding author: Dr Mary R. Sweeney, fax +353 1 7167407, email