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The Benefits of Breastmilk - Beyond Nutrients and Antibodies

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The value of breastmilk continues to grow as we discover additional properties and health benefits. It contains all the nutrients that a newborn requires, except for vitamin D, and life protecting antibodies that are custom made by mom in response to the unique dangers of her environment. However, recent research continues to uncover hidden treasures within this elixir of life. This article will review new studies and discuss the implication for infant development.

Breastmilk changes in response to baby’s cues

Benefits of Breastmilk

When infants are battling infection their mother’s milk appears to provide more white blood cells that are tailored specifically against the pathogen at hand (1). Exactly how mother’s body is notified of the infant’s distress is unclear (unless of course the mother is fighting the same microbe). One hypothesis is that some of the expressed milk that has encountered baby’s saliva is actually sucked back into the breast tissue. Here it is thought to alter the production of future milk by informing mom’s immune cells of baby’s peril. In this way, hormones, immune cytokines and oral microflora of the infant influence the immunological and nutritional content of mother’s milk. While ultrasound studies demonstrate retrograde movement of fats deeper into breast tissue from the areola, further research is needed to confirm this hypothesis.

There is melatonin in the breastmilk!

Benefits of Breastmilk

Melatonin is a hormone produced by the pineal gland (and other organs) during times of dark, in adults and young children. In infants, the production does not begin until the age of 3 or 4 months. While in utero, the baby depends on the placenta for its melatonin needs. Once born, it will depend on the breastmilk for its supply. Why is melatonin important for babies? There are several important features of melatonin. First, it can support immune function. A small study of infants battling sepsis, a severe for of infection, demonstrated protection and increased survival rates of infants who were given super high amounts of melatonin (orally 20mg divided into 10mg per dose) (2). Obviously, breastmilk contains only small amounts of melatonin compared to those used in the study but provided multiple times throughout the night on a regular basis it may offer some protection again infections as well. Melatonin in the breastmilk fluctuates with circadian rhythms. It is highest during the night and virtually none existent during the daytime. For this reason, researchers are considering developing nighttime baby formula with melatonin, to replicate the natural circadian production.

Second, melatonin in adults has been implicated in healthy bone maintenance. It has shown promise in animal studies of prevention of scoliosis (3); a condition characterized by poorly developed bones of the spine resulting in excessive curvature. Human studies demonstrate potential link between melatonin deficiency and development of scoliosis in adolescence (4). However, at this point whether melatonin influences bone development in infants is purely speculative. Lastly, melatonin can be produced in the digestive tracts of adults where it regulates gastrointestinal motility. Therapeutically, melatonin is used to treat gastroesophageal reflux disease and has potential use in the treatment of irritable bowel syndrome. In infants, melatonin may be the key to preventing colic. Studies report reduced colic in exclusively breast-fed infants and altered melatonin production in infants with colic (5).

It is not sterile

We have known for a while now that breastmilk influences the microflora of the digestive tract; promoting the colonization with health protecting bacteria. Apparently, the process of breastfeeding, not only the milk itself, is important. The flora of the skin contributes to the microbiological profile of the milk. This is evident in the studies that examine pumped milk and milk expressed via the nipple shield. The microflora that is delivered to the infant and is cultured from their stool is significantly different from milk delivered without any such devices (6). This makes sense, since during the feeding the baby must engulf the nipple and surrounding areola, thus coming in contact with a decent amount of skin and its respective inhabitants. The microbiological profile of breastmilk includes staphylococci, streptococci, micrococci, lactobacilli and enterococci (7). It remains to be explored where exactly these bacteria come from in mom’s body, aside from the local skin. One hypothesis is that they are transported to the breast from the gut. If true, this may provide an additional link between maternal diet and breastmilk composition.

Mother’s immune cells are passed with the breastmilk!

Previously, breastmilk was considered a source of passive immunity. Passive immunity offers temporary protection. Maternal antibodies pass into the infant and offer protection only while they are present in the body. Once weaning has occurred, the immune system was believed to remain untrained and naïve. It required exposure to infective organism in order to produce its own antibodies and long-term surveillance. However, we now learn that maternal immune cells, called T-lymphocytes, do make their way into the digestive tract of the infant where they set up shop and begin to train the local residents (8). The immune system of the gastrointestinal tract builds fortresses along the perimeter of the intestines called Peyer’s patches. These fortresses house a diverse range of immune cells whose job it is to police the intestines, prevent invasion and report to more central headquarters on their findings (for example the regional lymph nodes). Infant immune cells that reside in these are considered naïve. They haven’t seen much of the microbe world and are not great at distinguishing friend from foe.

Benefits of Breastmilk

Maternal cytotoxic T cells and T lymphocytes come to the rescue! Maternal lymphocytes travel to the Peyer’s patches and begin instructing the baby’s naïve immune cells. In this way, breastmilk effectively provides long term protection and acts as a source of active immunity. Active immunity is when the organism’s own immune system becomes engaged in the defence processes. Beyond protection against acute infections, this form of immune transference may play a protective role against chronic inflammatory conditions well into adulthood. Numerous studies highlight the importance of the digestive tract in regulating systemic immune response, shifting either towards or away from pro-inflammatory states. This hypothesis is supported by research that demonstrate breastfeeding correlating with reduced incidence of chronic inflammatory conditions such diabetes, obesity and cardiovascular diseases. In addition, maternal lymphocytes (or maternal microbes) may be protective against autoimmune conditions such as celiac disease, asthma and multiple sclerosis (9).

Breastmilk promotes cognitive development

Breastmilk contains several important growth factors including brain derived neurotrophic factor, nerve growth factor, glial cell lined-derived neurotrophic factor, fibroblast growth factor and many others (10). These growth factors are involved in regulating neurological development through facilitating growth of axons and dendrites and formation of new connections between neurons, called synaptogenesis. Additionally, these factors may be responsible for the maturation of the intestines, by supporting the development of the enteric nervous system. These growth factors are found in the breastmilk and vary in amount depending on the mother’s health. For example, women with pre-eclampsia deliver more brain-derived neurotrophic factors in their milk compared to women without this condition. This is thought to make up for the increased risk of development and cognitive challenges associated with this condition. In fact, breastfed infants (compared to formula fed) consistently score higher on various cognitive and developmental assessment tools, such as Bayley scale of infant development, IQ and total behaviour rating scale, compared to formula fed, which may be due to these growth factors.

Benefits of Breastmilk

Docosahexaenoic acid (DHA) is also found in breastmilk. This fatty acid can vary in amounts depending on mother’s diet and/or supplementation. DHA in breastmilk has been correlated with various health benefits for the infant. Improved vision may be explained by the fact that DHA can be found with the phospholipids of the retina. Since the nervous system is also highly dependent on fatty acids for its structure it is also of no surprise that DHA offers better neurological development to the infant, according to several studies (11). However, these findings are inconsistent, as several research papers report no benefit associated with this nutrient. This may be due to the complexity associated with researching breastmilk components, since as mentioned prior, breastmilk contains several important growth factors. Thus, it is difficult to control for all the confounding variables and/or to assess all the nutrients that are present in each participant’s sample. Given the latest research on the gut-brain connection, it is possible that the cognitive benefits provided by the breastmilk may be due to the microbiological profile contained in the milk.

In conclusion, breastmilk is great for many different reasons. Recent research demonstrates sophisticated immunological training through delivery of maternal T-lymphocytes and potentially through nocturnal melatonin. Melatonin may also be helpful in reducing colic, though further research on this required. Various growth factors and fatty acids are passed in the milk offering neuroprotective and neurodevelopmental benefits. No doubt as further research explores the impact of maternal diet and environmental exposure, we will expand our knowledge of all the benefits, and potential risks that breastmilk carries with it. This research may also help in developing better infant formula, which may be necessary when breastmilk is not available and/or is contraindicated.