Deborah O'Connor

Deborah O'Connor PhD, RD
Senior Associate Scientist, Translational Medicine, Hospital for Sick Children, Scientific Associate Staff, Department of Pediatrics, Division of Neonatology, Mount Sinai Hospital, Sinai Health System
Department of Nutritional Sciences
Contact Info
T: (416) 978-7235
F: (416) 978-5882
Medical Sciences Building, 5th Floor, Room 5253
1 King's College Circle
Toronto, ON, M5S 1A8
Appointment Status Primary
Accepting new students
PhD, University of Illinois
MS, University of Illinois
Dietetic Internship, Kingston General Hospital
BASc, University of Guelph


Research Synopsis

Our research program is focused on two broad areas of maternal and infant nutrition. First, we are interested in understanding the factors that affect the folate and one-carbon (e.g. vitamin B12) nutrient status of women, infants, and young children. In particular, we are investigating the role folic acid fortification, vitamin and mineral supplementation and colonic bacterial folate biosynthesis play on the folate status of women of reproductive age. Folate and other one carbon nutrients are critically involved in prevention of birth defects and emerging evidence suggests these nutrients also play important roles in epigenetic programming of adult disease.

Second, our research group is actively engaged in supporting human milk feeding of vulnerable infants—specifically the hospitalized infants who have unique nutritional requirements. We have been studying the clinical indications for pasteurized donor human milk when mother’s milk is unavailable and  the impact of feeding nutrient-enriched mother’s own and donor milk  during initial hospitalization and early after hospital discharge on the growth, body composition and development (cognitive and motor) of very low birthweight infants during the first 5 years. With our expert collaborators, we are investigatcoling the role that type of early feeding plays on the gut microbiome of the infants and how this may mediate short- and long-term health outcomes.

Publications and Awards

View PubMed search of this faculty member's recent publications.

Recent Publications

Pitino M, Stone S, O’Connor DL, Unger S. Is frozen human milk that is refused by mother’s own infant suitable for human milk bank donation? Breastfeeding Medicine 2019 Feb 21. doi: 10.1089/bfm.2018.0193. [Epub ahead of print]

Pitino M, Unger S, Doyen A, Pouliot Y, Aufreiter S, Stone D, Kiss A, O’Connor DL. High hydrostatic pressure processing better preserves the nutrient and bioactive compound composition of human donor milk. Journal of Nutrition 2019 Feb 15. pii: nxy302. doi: 10.1093/jn/nxy302. [Epub ahead of print]

Castro M, Asbury M, Shama S, Stone D, Yoon EW, O’Connor DL, Unger S. Energy and fat intake for preterm infants fed donor milk is significantly impacted by enteral feeding method. Journal of Parenteral and Enteral Nutrition. 43(1):162-165, 2019

Chan YM, Aufreiter S, O'Keefe SJ, O’Connor DL. Switching to a fibre-rich and low-fat diet increases colonic folate contents among African Americans. Applied Physiology Nutrition and Metabolism 44(2):127-132, 2019

Lamers Y, MacFarlane AJ, O’Connor DL, Fontaine-Bisson B. Periconceptional intake of folic acid among low-risk women in Canada: summary of a workshop aiming to align prenatal folic acid supplement composition with current expert guidelines. American Journal of Clinical Nutrition 108(6):1357-1368, 2018

Omand JA, To T, O’Connor DL, Parkin PC, Birken CS, Thorpe KE, Maguire JL. 25-hydroxyvitamin D and health service utilization for asthma in early childhood. Pediatric Pulmonology. 53(8), 1018-1026, 2018

O’Connor DL, Kiss A, Tomlinson C, Bando N, Bayliss A, Campbell D, Daneman A, Francis J, Kotsopoulos K, Shah P, Vaz S, Williams B, Unger S. Nutrient enrichment of human milk with human and bovine milk-based fortifiers for infants born weighing <1250 g: a randomized clinical trial. American Journal of Clinical Nutrition. 108(1):108-116, 2018

Barzilay E, Moon A, Plumptre L, Masih SP, Sohn KJ, Visentin CE, Ly A, Malysheva O, Croxford R, Caudill MA, O’Connor DL, Kim YI, Berger H. Fetal one-carbon nutrient concentrations may be affected by gestational diabetes. Nutrition Research. 55:57-64, 2018

Francis J, Unger S, Bando N, Vance A, Gibbins S, Kiss A, Church P, Sellen D, O’Connor DL. Post-discharge feeding of very-low-birth-weight infants: adherence to nutrition guidelines. Journal of Pediatric Gastroenterology and Nutrition. 67(3):401-408, 2018

Butcher J, Unger S, Li J, Bando N, Romain G, Francis J, Mottawea W, Mack D, Stintzi A, O’Connor DL. Independent of birth mode or gestational age, very low birth-weight infants fed their mothers' milk rapidly develop personalized microbiotas low in Bifidobacterium. Journal of Nutrition. 148(3):326-335, 2018

Elmekkawi A, O’Connor DL, Stone D, Yoon EW, Larocque M, McGeer A, Unger S. Impact of neonatal intensive care unit admission on bacterial colonization of donated human milk. Journal of Human Lactation. 34(2):350-354, 2018

Trang S, Zupancic JAF, Unger S, Kiss A, Bando N, Wong S, Gibbins S, O’Connor DL of behalf of the GTA DoMINO Feeding Group. Cost-effectiveness of supplemental donor milk versus formula for very low birth weight infants. Pediatrics. 141(3), 2018

Van der Plas E, Erdman L, Nieman BJ, Weksberg R, Butcher DT, O’Connor DL, Aufreiter S, Hitzler J, Guger S, Schachar RJ, Ito S, Spiegler B. Characterizing neurocognitive late effects in childhood leukemia survivors using a combination of neuropsychological and cognitive neuroscience measures. Child Neuropsychology. 24(8):999-1014, 2018

Plumptre L, Masih SP, Sohn KJ, Kim D, Visentin CE, Ly A, Berger H, Croxford R, O’Connor DL, Kim YI. Suboptimal maternal and cord plasma pyridoxal 5’ phosphate concentrations are uncommon in a cohort of Canadian pregnant women and newborn infants. Maternal and Child Nutrition. 14(1):e12467, 2018

Omand JA, To T, O'Connor DL, Parkin PC, Birken CS, Thorpe KE, Maguire JL. 25-hydroxyvitamin D and health service utilization for asthma in early childhood. Pediatric Pulmonology. 53(8):1018-1026, 2018 (Collaborator).

Omand JA, To T, O'Connor DL, Parkin PC, Birken CS, Thorpe KE, Maguire JL. 25-Hydroxyvitamin D, supplementation and health service utilization for URTI in young children. Public Health Nutrition. 20:1816-24, 2017

Ng D, Unger S, Asbury M, Kiss A, Bishara R, Bando N, Tomlinson C, Gibbins S, O’Connor DL. Neonatal morbidity count is associated with a reduced likelihood of achieving recommendations for protein, lipid and energy in very low birth weight infants: a prospective cohort study. Journal of Parenteral and Enteral Nutrition. 42(3): 2017

Yetley EA, MacFarlane AJ, Greene-Finestone LS, Garza B, Ard JD, Atkinson SA, Bier DM, Carriquiry AL, Harlan WR, Hattis D, King JC, Krewski D, O’Connor DL, Prentice RL, Rodricks JV, Wells GA. Options for basing dietary reference intakes (DRIs) on chronic disease endpoints: report from a joint US/Canadian-sponsored working group. American Journal of Clinical Nutrition. 105(1):249S-285S, 2017

Ng D, Brennan-Donnan J, Unger S, Bando N, Gibbins S, Nash A, Kiss A, O’Connor DL. How close are we to achieving energy and nutrient goals for very low birth weight infants in the first week? Journal of Parenteral and Enteral Nutrition. 41(3):500-506, 2017

O’Connor DL, Gibbins S, Kiss A, Bando N, Brennan-Donnan J, Ng E, Campbell DM, Vaz S, Fusch C, Asztalos E, Church P, Kelly E, Ly L, Daneman A, Unger S; for the GTA DoMINO Feeding Group. Effect of supplemental donor human milk compared with preterm formula on neurodevelopment of very low-birth-weight infants at 18 months: a randomized clinical trial. Journal of the American Medical Association. 316(18):1897-1905, 2016

Vanderhout SM, Birken CS, Parkin PC, Lebovic G, Chen Y, O’Connor DL, Maguire JL. Relation between milk-fat percent, vitamin D, and BMI z score in early childhood. American Journal of Clinical Nutrition. 104(6):1657-1664, 2016

Furlong KR, Anderson LN, Kang H, Lebovic G, Parkin PC, Maguire JL, O’Connor DL, Birken CS. BMI-for-age and weight-for-length in children 0 to 2 years. Pediatrics. 138(1): e20153809, 2016

Visentin CE, Masih S, Plumptre L, Schroder TH, Sohn KJ, Ly A, Lausman AY, Berger H, Croxford R, Lamers Y, Kim YI, O’Connor DL. Low Serum Vitamin B-12 concentrations are prevalent in a cohort of pregnant Canadian women. Journal of Nutrition. 146(5): 1035-42, 2016

Vanderhout SM, Birken CS, Parkin PC, Lebovic G, Chen Y, O’Connor DL, Macguire JL. Higher milk fat content is associated with higher 25-hydroxyvitamin D concentration in early childhood. Applied Physiology Nutrition and Metabolism. 41(5): 516-21, 2016

O’Connor DL, Blake J, Bell R, Bowen A, Callum J, Fenton S, Gray-Donald K, Rossiter M, Adamo K, Brett K, Khatri N, Robinson N, Tumback L. Society of Obstetricians and Gynecologists of Canada: Canadian Consensus on Female Nutrition-Adolescence, Reproduction, Menopause and Beyond. Journal of Obstetrics and Gynaecology Canada. 38(5):508-554, 2016

Panczuk JK, Unger S, Francis J, Bando N, Kiss A, O’Connor DL. Introduction of bovine-based nutrient fortifier and gastrointestinal inflammation in very low birth weight infants as measured by fecal calprotectin. Breastfeeding Medicine. 11(1): 2-5, 2016

DiLauro S, Unger S, Stone D, O'Connor DL. Human Milk for Ill and Medically Compromised Infants: Strategies and Ongoing Innovation. Journal of Parenteral and Enteral Nutrition. 40(6):768-782, 2016

Colapinto CK, O’Connor DL, Sampson M, Williams B, Tremblay MS. Systematic review of adverse health outcomes associated with high serum or red blood cell folate concentrations. Journal of Public Health. 38(2):e84-97, 2016

Kocel S, Russell J, O’Connor DL: Fat-modified breast milk resolves chylous pleural effusion in infants with post-surgical chylothorax but is associated with slow growth. Journal of Parenteral and Enteral Nutrition. 40(4):543-551, 2016


Non-Refereed Book Chapters and Reviews:      

Unger SL, Ewaschuk JB, O’Connor DL. Donor milk trials. In: Gastroenterology and Nutrition: Neonatology Questions and Controversies 3rd edition, edited by Poindexter BB, Neu J, Polin R. Elsevier, Philadelphia PA Chapter 5, 59-86, 2019

LeMay-Nedjelski L, Copeland J, Wang PW, Butcher J, Unger S, Stintzi A, O’Connor DL. Methods and strategies to examine the human breastmilk microbiome. Methods in Molecular Biology - Microbiome Analysis, edited by Beiko R, Parkinson J, Hsiao W. Springer. 2018

O’Connor DL, Trang S, Chan Y.M.: Nutrition issues during lactation. In: Handbook of Nutrition and Pregnancy 2nd edition, edited by Lammi-Keefe CJ, Couch SC, Kirwan JP. The Human Press Inc., Totowa, NJ, Chapter 4, 323-355, 2018


Honours and Awards

2016 Faith Elizabeth Winifred (Rusted) Bayley Nutrition Lectureship (Memorial University)

2015 Khursheed Jeejeebhoy Award, Canadian Nutrition Society

2014 Chair, Vitamin Research in Human Milk and Development, University of Toronto

2011 President’s Award Nomination, The Hospital for Sick Children

2011 Teaching Award: Graduate Student Mentorship (Runner-up), University of Toronto

2000 Pinnacle Award of Excellence, Ross Products Division, Abbott Laboratories