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I have heard that mother's milk is preferred over other baby foods, because it contains immunoglobulins (secretory IgA), and other essential nutrients.

But why is mother's milk so special? Any mammalian milk, such as the widely available cow's milk, should presumably have a similar composition as human milk? What makes mother's milk in specific so healthy?

Could the mere act of breastfeeding, in itself, lend to some beneficial outcome?

canadianer
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Mehul Sharma
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    I think I read a comment on the parenting stack exchange about this topic, and it spoke on the benefits of mother and child bonding. – Ro Siv Mar 12 '16 at 19:17
  • Was there a neuroendocrinological basis given for substantiating the bonding hypothesis ? – Mehul Sharma Mar 12 '16 at 19:19
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    Just taking the immunoglobulins alone, I would ask you this: do you think cows have immunoglobulins likely to match the needs of a human infant as precisely as the human child's own mother (same pathogens, same environment, etc.) or that a cow's immunoglobulins are more likely a better match for that cow's own offspring? This goes across the board for all mammals in all differing locations (i.e. a mother's milk in Malaysia will have a different antibody composition than one in, say, Canada. – anongoodnurse Mar 12 '16 at 21:33
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    Anecdotal evidence (n=1): My 3yo daughter caught chickenpox and we have a 5 month old baby too. They are often close together and touch a lot. Baby is breastfed by mother who had chickenpox already (so she has antibodies). Baby is breastfed and didn't catch the (highly infectious) chickenpox. – Tomáš Kafka Mar 13 '16 at 03:17
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    @TomášKafka: you seem to be into something. WebMD endorses your anecdotal evidence: http://www.webmd.com/vaccines/tc/chickenpox-varicella-what-happens (2nd bullet point). – Quora Feans Mar 13 '16 at 23:19
  • Cow's milk is not human milk. Starting with the percentages of fat to protein alone, the differences are immense. Evolutionarily, it makes no sense to surmise that milk from one species is just as suited for the offspring of another. Cow's milk evolved to feed calves. Human's milk evolved to feed humans. And the needs of calves are apparently quite different than the needs of infants. –  Mar 14 '16 at 07:09
  • @TomášKafka I don't know of any studies, but this is a very common belief, that the mother's immune strengths are passed to the infant's while breast feeding. If true, this means infants are immune to all that the mother is immune to. Alas, nothing is really that simple. If there is any truth to it, it probably varies by disease, geography, age, race, and everything else too. –  Mar 14 '16 at 07:14
  • @fredsbend I think you're just simplifying to the point of basically attacking a strawman. It's been observed that some antibodies (and other immune system-related "stuff") are passed to the child in milk, and some of them survive the infant's digestive system. Some is the key word, of course - it's nowhere near 100% effective, and it still depends on the baby's own immune system. The kid just gets a headstart on the markers, giving it a much better chance of coping with the infection - provided the mother is also exposed to the same infection (whether she gets sick or not). – Luaan Mar 14 '16 at 08:31
  • @TomášKafka When I was two or three years old my brother (older by three years) caught chickenpox at school. My mother had already had it but my father and I hadn't had it yet. My brother had a bit of a temperature and a lot of spots. My dad became very sick with a fever and a lot of spots. Because I was so young I only got a few spots and no temperature. Neither my brother nor I were protected by my mother having chickenpox before we were born. It's more likely that your baby got it but showed no symptoms. – CJ Dennis Mar 14 '16 at 09:44
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    @anongoodnurse Adding to the issue of immunoglobulins; pasteurization (which is performed basically on all milk sold to consumers) will decrease the amount of immunoglobulins quite a bit. So even if immunoglobulins from cow's milk would be useful, they are mostly lost in pasteurized milk. Related, Chantry et al. (2009, J Acquir Immune Defic Syndr.) is studying the effect of flash-heat pasteurization on immunoglobulins in human breast milk, since flash-heating is used as a way to reduce vertical HIV transmission. – fileunderwater Mar 18 '16 at 13:05
  • Well, I can't say necessarily mother's milk. It is possible for a woman to feed the child that is not born by her. And I can't say that mother's milk in this case gives an advantage over other woman's milk. – rus9384 Oct 31 '18 at 15:08

2 Answers2

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The phrase "Breast is best" is a hotly debated one (source: The Guardian and personal communications with many folks). The reason why we don't want to feed infants cow's milk is, however, anything but debated, because

Cow's milk does not provide enough:

  • Vitamin E
  • Iron
  • Essential fatty acids

And because it contains too much:

  • Protein
  • Sodium

  • Potassium (source: NIH's MedLine)

  • Further, mother's milk is generally free of pathogens, cow's milk may not be (source: Australian Unity). However note that, unfortunately, HIV can hitchhike within the maternal white blood cells to the infant (Quintanilla, 1996)

There are many benefits to mother and infant of breast milk. These benefits are, however, typically compared to the benefits over formula. No study will compare the benefits of mother's milk over cow's milk, simply because infants should never be fed cow's milk.

The benefits of breast milk for the infant are the following:

  • Breast milk a nearly perfect mix of vitamins, protein, and fat, all provided in an easily digestible form, as compared to formula;
  • Breastfeeding lowers baby's risk of having asthma or allergies;
  • Plus, babies who are breastfed exclusively for the first 6 months, without any formula, have fewer ear infections, respiratory illnesses, and bouts of diarrhea. They also have fewer hospitalizations and trips to the doctor (source: WebMD).
  • Breast milk contains a variety of growth factors, including EGF, BDNF and GDNF that may promote vascularization and neural development (Ballard & Morrow, 2014).

There are a host of immunoprotective factors present in breast milk. These proteins offer protection against diarrhoea, food allergies and infections. The immunoprotective components of human milk include, but are not limited to:

  • Lactoferrin : binds to iron, thus rendering it unavailable to viruses, fungi and bacteria, which is an effective means of inhibiting their growth (Ballard & Morrow, 2014);
  • Lysozymes: destroy viruses and bacteria by disrupting their integrity (source: NIH's MedLine);
  • Secretory IgA: immunoglobulins that destroy viruses and bacteria. Secretory IgA is believed to survive the harsh conditions of the intestines, especially in infants and is therefore active in the intestines of the baby. IgA can bind to pathological viruses and block their receptors necessary to invade the epithelial cells lining the intestinal wall. It also clumps bacteria together through cross-linking, which may affect their dispersion. Bacterial cell membranes, like shown in Salmonella, may be disrupted by IgA binding (Mantis et al., 2011). As mentioned by anongoodnurse in the comments; because mother and baby share the same habitat and hence encounter the same pathogens, the antibodies produced by the mother will be more beneficial to the baby than any other mammal on earth;
  • Human milk contains a variety of chemokines and cytokines that can cross the intestinal barrier, where they communicate with baby's cells to influence immune activity. Many cytokines and chemokines have multiple functions, and milk-borne cytokines may be grouped broadly into those that enhance inflammation or defend against infection, and those that reduce inflammation (Ballard & Morrow, 2014);
  • Bifidus factor: promotes the growth of beneficial bacteria in the gut and limits the growth of disease-causing bacteria (source: NIH's MedLine).

  • A variety of immune cells, including macrophages, T cells, stem cells, and lymphocytes. In early lactation, the breastfed infant may consume as many as 1010 maternal leukocytes per day. They can differentiate into dendritic cells that stimulate infant T-cell activity (Ballard & Morrow, 2014).

  • Breast milk changes in composition according to the infant's needs, something cow's milk can never accomplish; The first fluid produced by mothers after delivery is colostrum, which is distinct in volume, appearance and composition. Colostrum is produced in low quantities in the first few days postpartum and is rich in immunologic components such as secretory IgA, lactoferrin, leukocytes, as well as developmental factors such as epidermal growth factor. It contains relatively low concentrations of lactose, indicating its primary functions to be immunologic and trophic rather than nutritional. Levels of sodium, chloride and magnesium are higher and levels of potassium and calcium are lower in colostrum than later milk (Ballard & Morrow, 2014).

For more complete reviews on the immunochemistry of breast milk, please refer to Ballard & Morrow (2014) and Mantis et al. (2011)

The mother also benefits:

  • Breastfeeding burns extra calories, so it can help mothers to lose pregnancy weight faster;
  • Breast feeding releases the hormone oxytocin, which helps the uterus return to its pre-pregnancy size and may reduce uterine bleeding after birth;
  • Breastfeeding lowers the risk of breast and ovarian cancer. It may lower the risk of osteoporosis;
  • Breastfeeding has been linked to higher IQ scores in later childhood in some studies (source: WebMD);
  • During lactation, menstruation ceases, offering a form of contraception;
  • Mothers who breastfeed are less likely to develop breast cancer later in life;
  • Breastfeeding is more economical than formula feeding;
  • Hormones released during breast-feeding create feelings of warmth and calm in the mother (source: NIH's MedLine).

In terms of bonding:

  • Skin-to-skin contact during breastfeeding, and eye contact all help a baby bond with the mother and feel secure.
  • Oxytocin release is known to promote the bonding with bubba. A newly born person can cause dramatic changes in the life of mommie (and daddy!), and a steady release of oxytocin promotes the bonding and love of mommie for the bubba (source: WebMD).

References
- Ballard & Morrow, Pediatr Clin North Am (2013); 60(1): 49–74
- Mantis et al., Mucosal Immunology (2011) 4: 03–611
- Quintanilla, Nurs Times, (1996); 92(31): 35-7

canadianer
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AliceD
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    I think this answer is very good; I'm not likely to top it for scope. The only thing I would add is more about antibodies and other contributors to immune function. (If you're interested, I left a comment under the question.) Here's another open source NIH paper that goes into more detail. +1 – anongoodnurse Mar 12 '16 at 21:30
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    It should also be noted that (various levels and kinds) of milk allergy are rather common in infants, so for an interesting portion of the population, cow milk simply isn't a substitute even when combined with a formula. Often the mother has to avoid milk products as well, since enough of the protein makes it to the breast milk. And many formulas contain cow milk as well, so you're stuck with the very expensive ones tailored for infants with allergy. – Luaan Mar 13 '16 at 12:59
  • +1 for a good and complete answer for the benefits of mothers milk. However as you stated yourself the issue is hotly debated. It would be nice to also add some disadvantages of breast-feeding. One example: producing milk is an energy-consuming process that slows down the recovery of the mother after giving birth. (Sorry no reference). – RHA Mar 13 '16 at 16:11
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    @RHA while it's an interesting subject, I think that's outside the scope of a question that's about whether milk from other mammals wouldn't be as good as breastmilk. – YviDe Mar 13 '16 at 18:32
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    @RHA (sorry, deleted the first comment to rephrase) except for the "Breastfeeding is more economical than formula feeding", I find this answer to be mostly focused on human vs animal milk. True, some points are independent of what sort of milk it is and relate to breastfeeding specifically (and wouldn't apply to pumping, for example), but other than that, I seem to be reading the answer different than you are. – YviDe Mar 13 '16 at 18:38
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    @RHA A working brain is also very energy-consuming. Should that be included in its disadvantages? // Child bearing by healthy women does not customarily require immediate "recovery" and it's completely not a given that stopping breast-feeding will have any positive clinical effect on the mother's "recovery". Not using up what your body wants to give away might in fact be determental to the overall health. – A.S. Mar 14 '16 at 09:16
  • Actually, menstruation ceases when breastfeeding for some time. The woman will be fertile despite breastfeeding after a while. http://www.llli.org/nb/nbsepoct06p196.html – Stilltorik Mar 14 '16 at 13:30
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    The point on pathogen transmission via milk is not really correct as you yourself have contradicted the point with the HIV example. There are many other pathogens that can be transmitted via milk. The issue with animal milk is that it may be difficult to check if the animal was infected. – WYSIWYG Mar 15 '16 at 06:16
  • I think the central point that would emerge from the entire picture is that the milk composition of a species is evolved such that it improves the fitness of that species. Buffalo milk has high fat and proteins compared to cow's milk but buffalo also produces lesser offspring (and a higher gestation period). A nutrient rich milk will ensure the calf's health/development and survival. So, in short, the milk composition is optimized according to the dietary/health requirements of the corresponding species. – WYSIWYG Mar 15 '16 at 06:22
  • @WYSIWYG - that's the debate. Nutritional value can be artificially reproduced. It's the immunological factors that are species and even individual specific. That's the point. – AliceD Mar 15 '16 at 06:45
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    Aw, the bonding bit was nice. Quite scary how busy life, might then interfere and disrupt these potential bonding opportunities... – hello_there_andy Mar 17 '17 at 13:40
  • Lysozyme degrades bacterial cell walls, it does not affect viruses. – canadianer Mar 17 '17 at 18:11
  • To further emphasize colostrum, infant have very weak immune systems early on and the supplimentation by the breastmilk is very helpful. – John Mar 17 '17 at 18:27
  • I think it would be better to cite this regarding HIV transmission: https://www.advancesinpediatrics.org/article/S0065-3101(07)00015-1/fulltext#sec4.5.6 – abukaj Aug 08 '19 at 11:27
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The contents of milk differ between species. For your example, cow's milk:

Infants fed WCM [Whole Cow's Milk] have low intakes of iron, linoleic acid, and vitamin E, and excessive intakes of sodium, potassium, and protein

Calves have different nutrition needs from human babies. Infants who receive cow's milk instead of breastmilk often suffer from iron deficiency (anemia).

As for antibodies, human babies will benefit the most from antibodies that help against diseases infecting humans, which are not the same as those infecting cows.

YviDe
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  • Calves have different nutrition needs from human babies. You hit the exact point, IMO. It applies for every species. – WYSIWYG Mar 15 '16 at 06:25