Newborns & Immune Health: Beyond Breastfeeding and Immunizations

 In Pediatrics, Women's Health

Sunita Iyer, ND, LM

Tolle Totum

I have both the privilege and challenge of working with families in the preconception, perinatal, and postpartum stages of parenting. This means that I encounter a great deal of excitement, wonder, and oftentimes fear. The fear may be about the impact of pregnancy, birth, or postpartum upon the parents and their changing lives. More often than not, the fear is rooted in their newborn’s health. Most of us who care for newborns and young infants can testify that the level of parental concern regarding their infants’ well-being, “doing it right,” and setting them up for a healthy life is present nearly every moment.

As a primary care, family medicine, and pediatric provider, the topics that figure highly into discussions about a newborn baby’s immune health include breastfeeding optimization and immunization practices. Within our profession and in the world around us, there are many heated and controversial conversations to be had on both of these topics. And yet, there exist very clear foundations in research and guidelines regarding how both breast milk and immunizations can positively affect a newborn’s health in the face of exposure and illness.1 In other words, as part of the preventive care we offer, they are well-established components of our tool kits.

So, what else can we offer that is both compelling and effective?

Vitamin D Levels

Many providers who work with newborns, and even with the families prior to a baby’s birth, have discussions about vitamin D supplementation. This discussion often covers adequate supplementation for the pregnant parent prior to birth, in the postpartum period and during breastfeeding, as well as direct administration to the newborn. The typical dosing guidelines for pregnant and nursing women list a range of 2000-6600 IU daily, depending on 25-hydroxy (OH) vitamin D levels, ethnicity and skin color, season and sun exposure, and other health or lifestyle factors; an average effective dose is thought to be 4000 IU daily.2,3 The typical dosing recommendation for newborns to maintain adequate vitamin D levels is at least 400 IU daily. Interestingly, a 2017 study by Umaretiya et al indicated that parents would much prefer to supplement themselves than to supplement their babies directly.4 So, getting clear on how babies can best maintain adequate levels is incredibly important.

This may seem simplistic to many naturopathic, integrative, and conventional providers alike, given the breadth of research and mainstream information on vitamin D. However, what seems to be absent from many discussions of vitamin D supplementation for newborns is the impact of adequate vitamin D levels on immune health, as opposed to just calcium absorption and rickets prevention.

Why is vitamin D so critical to the immune health of newborns? The implications of maternal and infant vitamin D status on the development of type 1 diabetes, autoimmunity, asthma, and allergies in children are well established. However, focus on the immediate newborn and infant period brings additional research into view.5,6 Findings from more than 1 study demonstrated that vitamin D deficiency in newborns affects their susceptibility to and recovery from respiratory infections in the months immediately following birth.7,8 Newborns with optimal vitamin D status experience fewer acute office and emergency room visits, less use of therapeutic steroids in the management of respiratory syncytial virus (for which immunization is unavailable) or bronchiolitis, and generally less distress (including their parents).9-11

Being in the business of prevention and as a provider to whole families, this seemingly small “win” is enormous. Bronchiolitis as a consequence of respiratory syncytial virus (RSV) is common in children under 2 years of age and is the most common reason for hospitalization of infants.1,7 Anything we can do to keep babies out of the hospital in those days and months after their birth is clearly more than just a benefit to immune health.

The Microbiome

The clinical significance of that diverse community of organisms inhabiting our intestinal tracts is quickly gaining traction in mainstream medical circles as research increasingly focuses on the relationship of a healthy microbiome to digestion, mood, chronic illness and autoimmunity, asthma, and allergies. Again, it may seem simplistic to those providers who have long been discussing the GALT (gut-associated lymphoid tissue), the microbiome, its relationship to TH1/TH2 balance, and overall immune resilience and health. Appreciation for the role of the gut microbiome in health is growing among conventional practitioners. However, simply stating to families that taking “good bacteria” is a good idea and that probiotics can help nearly everything doesn’t get specific enough in terms of newborn health. What do parents actually need to know about how a healthy, diverse, and functional intestinal community affects their newborn babies?

Current research into neonatal and infant gut colonization suggests “vertical transmission” via vaginal birth and breast milk.5,12 Such research has influenced hospital-based intrapartum, postpartum, and neonatal care practices that encourage vaginal birth, discourage routine bathing of babies following delivery, and initiate and support breastfeeding; all of these measures assist in timely and proper establishment of a health microbiome in the infant’s body.5,6,12,13 Among newborns with a well-established microbiome (typically occurring at about 1 week of age), we see many of the same positive, longer-term outcomes as with adequate vitamin D levels, such as less atopic disease and allergies, less asthma, and less obesity.6 Although supplementation of newborns with specific probiotic bacterial strains can aid in the development of a healthy microbiome and prevention of acute gastrointestinal disorders, probiotic supplementation – in contrast to vitamin D – has not yet been shown to prevent acute respiratory illness.

Vitamin D may represent a critical link between probiotics, the microbiome, and acute respiratory illness in neonates. In a study investigating the effect of the probiotic strain Lactobacillus reuteri on levels of serum cholesterol and fat-soluble vitamins in hypercholesterolemic adults, vitamin D3 levels were shown to increase by 25.5%.14 You may recall that L reuteri is considered the probiotic strain most beneficial in the treatment of infant colic,5 so if we want to consider a “twofer” in our approach to newborn immune health, using L reuteri should certainly be in the running.

Maternal Depression

Working with newborns means that we are also working with parents. It may not always mean that the parents are officially our patients, but to adequately care for new babies we must be checking in with the parents and evaluating their well-being. The American Academy of Pediatrics recommends that we assess for maternal postpartum depression as part of routine pediatric care.15 For most of us, the link between a physically, mentally, and emotionally-well parent and a well newborn seems obvious. Aside from biochemical transmission during pregnancy and breastfeeding, there are myriad ways in which women can transmit mood, social cues, and behavior to babies, both in utero and as newborns. Most of this information relates to the development of depressive symptoms in the offspring as babies or children, or even later as adults.

Vitamin D constitutes another possible link between mood and immune health, the supplementation of which may help to prevent potential problems in newborns. In a recently published study by Zhou et al, a significant relationship was observed between maternal depressive symptoms, low winter-spring levels of 25(OH) vitamin D, and low neonatal vitamin D levels.16 It was thought that maternal depression might actually decrease transmission of vitamin D through the placenta, a mechanism that might have been masked somewhat in the summer months when depressive symptoms were less.16 The findings of this study provide another lens through which to view parents’ wellness, particularly depression, and how it can impact newborn wellness.


Although vitamin D, the microbiome, and mood may be “old news” among naturopathic doctors, it is not always so with the parents under our care. At the same time, the more that families hear about vitamin D or probiotics for immune health, the more they can seem like a “fad” that warrants little attention. However, any intervention that can possibly prevent severe respiratory illness and hospitalization of an infant is certainly worth more attention than just a fad. Optimizing vitamin D levels during pregnancy, considering direct vitamin D supplementation for newborns, using specific bacterial strains in the form of probiotics, and fully addressing parents’ depressive symptoms represents a multi-factorial approach that can alter the overall picture of newborn and family wellness.


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  12. Pannaraj PS, Li F, Cerini C, et al. Association Between Breast Milk Bacterial Communities and Establishment and Development of the Infant Gut Microbiome.JAMA Pediatr.  2017 May 8. doi: 10.1001/jamapediatrics.2017.0378. [Epub ahead of print].
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  15. Earls MF; Committee on Psychosocial Aspects of Child and Family Health American Academy of Pediatrics. Incorporating recognition and management of perinatal and postpartum depression into pediatric practice. Pediatrics. 2010;126(5):1032-1039.
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Image Copyright: <a href=’’>alenkasm / 123RF Stock Photo</a>

Sunita Iyer, ND, LM, is a licensed primary care naturopathic doctor and licensed midwife in the state of Washington. Dr Iyer earned her doctorate and midwifery training from Bastyr University. She is currently in active clinical practice and is on faculty at the University of Washington Bothell. Dr Iyer holds particular interests in pediatrics, women’s health, and preconception and perinatal care. She loves treating whole families from beginning to end, and enjoys a bit of the “town doctor” life. With her better half, Dr Iyer runs an integrative clinic, Eastside Natural Medicine, in Kirkland, WA, and practices alongside many incredibly talented colleagues who share the love of caring for and encircling families.

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