Immunological Research and Breastfeeding Beyond Infancy

[elanorh]

Spin-off of a discussion in another thread here:

I've been looking for primary literature on extended breastfeeding for my own interest recently (because I am wondering how to balance nursing with TTC #2 for the future - don't want to shortchange DD on the BM but don't want to wait too long on the TTC either). I haven't been able to find much.

Anyone with information or questions in this area, let's discuss here. The question posited was - once the infant gut 'locks up' at around 6 months, are any of the immune components in breastmilk accessible by infants/children?

Links to primary sources are especially helpful.

I don't work in a medical field, so my knowledge of cell structure/size/ etc. as we discuss this is minimal. Hopefully those with more knowledge in that area and in the function of the human immune system, will join in.

I did find this article which discusses the immune components in human breast milk, with citations of additional articles about it (ie, there is minimal discussion of the antimicrobial properties of breast milk, but a citation of other research already conducted in that area).

http://jn.nutrition.org/cgi/content/full/135/1/1
(The above source is the Journal of Nutrition)

ETA: My understanding had always been that there was scientific consensus about the immune assistance that breastmilk provides, throughout infancy and into toddlerhood etc., per the WHO and AAFP statements, among other things.

ETA2: Just wanted to note for the record, this thread is not intended at all as a critique of the 'worth' of breastfeeding beyond infancy. I have breastfed both my children past 2 1/2 (and counting for dd2 who is three). I think we can all agree that there are a multitude of factors which make breastfeeding beyond infancy something worth working towards and supporting - whether we are looking at nutrition, physiological expectations, comfort, etc. etc. etc. I do think that for some mothers, being able to emphasize the immune benefits of breastfeeding is a favorite argument to use with relatives, friends, coworkers who are critical of breastfeeding beyond 12 months. Therefore, seeing that there were some who doubted whether there is any immune benefit after six months, I thought it would be good to gather research and discuss here.

[mambera]

Hi, I followed you here.

Here is the original thread for those who missed the beginning of this discussion:
http://www.mothering.com/discussions...php?p=14700755

Originally Posted by elanorh

I did find this article which discusses the immune components in human breast milk, with citations of additional articles about it (ie, there is minimal discussion of the antimicrobial properties of breast milk, but a citation of other research already conducted in that area).

http://jn.nutrition.org/cgi/content/full/135/1/1
(The above source is the Journal of Nutrition)

That's a really good summary and I think it's pretty educational. It does restrict the discussion to infants, and I agree with you that the immunological benefits for infants are pretty clear.

I'm more curious about the evidence base for health benefits in children over a year. (As I mentioned on the other thread, I became interested in this question bc I want to be informed about whether weaning in order to TTC would adversely affect my DD's health.)

My understanding had always been that there was scientific consensus about the immune assistance that breastmilk provides, throughout infancy and into toddlerhood etc., per the WHO and AAFP statements, among other things.

I think there's scientific consensus for benefit *up to* one year. As I said on the other thread, I've found barely anything that addresses benefits *after* one year, and what I have found suggests that any benefits would be more emotional/intangible than measurable health benefits.

One problem is that so few women breastfeed past one year that it's difficult to study. Also, those who do breastfeed past a year are likely to have a multitude of social/lifestyle characteristics that set them apart from those who wean early, and it would be really difficult to tease apart the effects of extended BF'ing per se from the effects of these other characteristics.

Just wanted to note for the record, this thread is not intended at all as a critique of the 'worth' of breastfeeding beyond infancy.

Ditto - since I'm the maverick who brought up the question, I thought I'd just state for the record that I am extremely pro-BF'ing (as is pretty much everyone on this site, heh). I do want to be informed about whether there are diminishing returns after a certain point though.

[elanorh]

I didn't think that the Journal of Nutrition article restricted its discussion to 'infants' in re: the immune factors in breast milk - it talked about the immune factors in breast milk. There was an aside on one of the subtopics about how that particular factor changed between colostrum and so on.

I know that breast milk banks don't want milk from mothers whose babies are over a year of age when the milk is pumped; I'm not sure why. Perhaps because the make-up of the milk has changed substantially enough that it's not what a newborn would need??

You're right in that extended breastfeeding is uncommon enough in the United States that research on it and its benefits would be difficult. However, I think the stereotypical 'hippie mother' who is breastfeeding beyond infancy stereotype (eating organic foods and whole grains, kid involved in a local AP playgroup, yadayada) - doesn't fit in the end. I've been startled by the friends I know who have breastfed, sometimes beyond three years of age - some of whom in every other way fit the stereotype of the "driven career woman" and aren't exactly serving up organic anything in their homes. I don't think there are as many commonalities as we assume in extended breastfeeding dyads -- I think a certain subset of us are more likely to 'out' ourselves as breastfeeding beyond infancy; but that doesn't mean that there aren't other mothers out there doing the same thing, KWIM?

I wonder whether any research has been done in Scandinavia on breastfeeding beyond infancy - that would remove the "But it's a Developing nation," argument about why breastfeeding beyond a year has been demonstrated as a protective factor for children.

[mambera]

Originally Posted by elanorh

I didn't think that the Journal of Nutrition article restricted its discussion to 'infants' in re: the immune factors in breast milk - it talked about the immune factors in breast milk. There was an aside on one of the subtopics about how that particular factor changed between colostrum and so on.

OK, but they do use the word 'infant' throughout the paper, and don't specifically discuss older children.

As I said above, I don't doubt that human milk does contain many immune factors (as do most other bodily secretions), and I think it's clear that young babies benefit immunologically from the breast milk.

What's not clear is whether these components fulfill an immunological function in older children. Only two of them (leukocytes and IgA) have been studied over time (in the Goldman papers from Acta Paediatrica Scandinavica that get cited everywhere), and it's been found that they are high in the first few month and drop to a steady level thereafter.

Based on what I know about gut absorption I'd guess that the utility of these things for the infant drops drastically after the gut closes; and the data I've been able to find (which are thin) mostly suggest that there is neither medical benefit nor harm to continued breastfeeding after 1 year.

I think the stereotypical 'hippie mother' who is breastfeeding beyond infancy stereotype (eating organic foods and whole grains, kid involved in a local AP playgroup, yadayada) - doesn't fit in the end. I've been startled by the friends I know who have breastfed, sometimes beyond three years of age - some of whom in every other way fit the stereotype of the "driven career woman" and aren't exactly serving up organic anything in their homes.

Hm... yes... some might consider me the 'driven career woman' as well, heh. I've never thought of it as particularly tied to my eating habits, but I could be wrong.

Anyway, that aside, actually I was thinking more about issues like maternal socioeconomic status and IQ, which correlate highly both with BF in the first place and with duration of BF, at least in the US. Actually I've read that it now seems that much of what was initially thought to be an IQ benefit of breastfeeding may be mostly an IQ benefit of being born to the kinds of mothers who breastfeed (smart ones with high socioeconomic status).

(Anyone who cruises justmommies.com - home to many mommies both BF and FF - may notice, incidentally, that the grammar, vocabulary, and literacy on MDC (where pretty much everyone is either EBF or trying like hell to do so) blows them out of the water. Just sayin'.)

[geekgolightly]

Originally Posted by mambera

What's not clear is whether these components fulfill an immunological function in older children. Only two of them (leukocytes and IgA) have been studied over time (in the Goldman papers from Acta Paediatrica Scandinavica that get cited everywhere), and it's been found that they are high in the first few month and drop to a steady level thereafter.

Although leukocytes and IgA do drop off, lysozyme rises.

http://www.kellymom.com/nutrition/mi...nefactors.html
See table Concentration of Immunologic Components in Human Milk


Also, not immunologic, but still interesting.

http://pediatrics.aappublications.or...act/116/3/e432

Fat and Energy Contents of Expressed Human Breast Milk in Prolonged Lactation -- Mandel et al. 116 (3): e432 -- Pediatrics

Objective. To estimate fat and energy contents of human milk during prolonged lactation.

Methods. Thirty-four mothers, of term, healthy, growing children, who had been lactating for >1 year (12–39 months) were recruited. Control subjects were 27 mothers, of term infants, who had been lactating for 2 to 6 months. Fat contents of the milk samples were estimated as creamatocrit (CMT) levels. Energy contents of the milk were measured with a bomb calorimeter.

Results. The groups did not differ in terms of maternal height and diet, infant birth weight, gestational age, or breastfeeding frequency. They differed significantly in terms of maternal age, maternal weight, and BMI. The mean CMT levels were 7.36 ± 2.65% in the short-duration group and 10.65 ± 5.07% in the long-lactation group. The mean energy contents were 3103.7 ± 863.2 kJ/L in the short-duration group and 3683.2 ± 1032.2 kJ/L in the long-duration group. The mean CMT levels and mean energy contents were correlated significantly with the duration of lactation (R2 = 0.22 and R2 = 0.23, respectively). In multivariate regression analysis, CMT levels (or energy contents) were not influenced by maternal age, diet, BMI, or number of daily feedings but remained significantly influenced by the duration of lactation.

Conclusions. Human milk expressed by mothers who have been lactating for >1 year has significantly increased fat and energy contents, compared with milk expressed by women who have been lactating for shorter periods. During prolonged lactation, the fat energy contribution of breast milk to the infant diet might be significant.

[witchygrrl]

What about Gulick, 1986 and Hamosh, 1991? They're referenced here:
http://www.kellymom.com/store/freeha..._factsheet.pdf

[mambera]

Originally Posted by witchygrrl

What about Gulick, 1986 and Hamosh, 1991? They're referenced here:
http://www.kellymom.com/store/freeha..._factsheet.pdf

The title of the Gulick paper sounds really interesting and I would love to read it. It may be exactly what I want to see (an examination of the health status of breastfed vs non-breastfed toddlers).

Unfortunately it is so old that I can't get it (pdfs available online only from 1995 onward, and this paper is from 1986). PubMed doesn't even have an abstract.

Anyone who has a pdf of the Gulick paper, I'd love love love if you could pass it along.

Regarding the question of 'are there antibodies in the milk' (which the Hamosh book is quoted to back up), I think we all know the answer is yes. What's not clear to me is whether there are documented health benefits to toddlers consuming the milk.

[witchygrrl]

Obviously, what needs to happen is a new study. Perhaps a follow up study of the kids from Gulick's paper, and a new one.

The big problem is of course the sheer immensity of confounding factors. But I think we have a pretty good amount of mammas heer who might be willing to commit to a study? Where else would you find so many extended breastfeeders in one place? Now if only we can find a researcher into immunology who wants to do this as a study. (I'm a lingust, so I'm out).

[witchygrrl]

I also found this abstract about breastfeeding and leukemia:
http://linkinghub.elsevier.com/retri...40673688928358

I don't have access to the whole thing, sadly.

[mambera]

Originally Posted by witchygrrl

I also found this abstract about breastfeeding and leukemia:
http://linkinghub.elsevier.com/retri...40673688928358

I don't have access to the whole thing, sadly.

That's a good one too - I'm interested in all kinds of health benefits. Actually from what I've seen, the link between early weaning and childhood cancers is reasonably well established.

But like most studies I've seen on these topics, this leukemia paper has a single category for babies who were BF from 6 months on (they divide into never-bf, weaned before 6 months, and weaned after 6 months).

In most of the studies I've seen, children who are bf past 1 year are a small population who are lumped into the 'past-6-months' cohort. So there's no way to tell whether there is a specific benefit of breastfeeding past a year.

[calpurnia]

interesting thread. i'm watching, though i have nothing to add...

[gen24]

I know it's not scientific, but here is a quote from Dr.Sears' The Vaccine Book:"Breast milk has antibodies that coat the lining of the nose, lungs, and intestine, so most germs that get inhaled or swallowed are killed. When I see patients in the office who tell me they don't want their baby to get vaccines, my first response is "I hope you plan to breastfeed your baby for at least 2 years!"

[Baby_Cakes]

[mambera]

OK, here is an excerpt from the WHO guidelines on breastfeeding - full text at

http://whqlibdoc.who.int/paho/2004/a85622.pdf

I figure they should cite the research on which they're basing their decision.

Although the impact of breastfeeding past the first year of life on infant appetite and growth has been controversial (Caulfield etal., 1996; Habicht, 2000), recent longitudinal studies demonstrate that in developing countries, a longer duration of breastfeeding is associated with greater linear growth when the data are analyzed appropriate-
ly to eliminate the influence of confounding variables and reverse causation (Onyango et al., 1999; Simondon et al, 2001).

(*I looked at these studies; the Onyango study is from western Kenya and finds that "the strongest association between breast-feeding and linear growth was observed in households that had no latrine and daily water use of less than 10 liters/person."
The Simondon paper is from Senegal; its abstract says "Prolonged breast-feeding is frequently associated with malnutrition in less-developed countries... Prolonged breast-feeding improved linear growth, and the negative relation between height-for-age and duration of breast-feeding was due to reverse causality."




A longer duration of breastfeeding has been linked to reduced risk of childhood chronic illnesses (Davis, 2001) and obesity (Butte, 2001), and to improved cognitive outcomes (Reynolds, 2001), although the causal relationships underlying these associations remain controversial.
Most of these studies have not specifically examined the effect of breastfeeding beyond 12 months on these outcomes.

This pretty much echoes what I'm finding out on my own: Different studies show different outcomes on growth, but the data lean slightly towards better growth and health outcomes in children bf longer - where 'longer' generally means up to 1 year, since minimal data are available beyond that point. They don't mention any studies specifically targeted towards bf past one year, and they don't even bother citing the Gulick paper. (I suspect that means it was really small or poorly done, or unreliable for some other reason.)

[BarefootScientist]

Subbing as I am very interested. I have nothing to add right now but I have always wondered how exactly antibodies would have an effect after the gut closed, since they are proteins and I assume would simply be digested...but this is not my area of expertise so I could very well be wrong.

[Megan73]

Originally Posted by BarefootScientist

Subbing as I am very interested. I have nothing to add right now but I have always wondered how exactly antibodies would have an effect after the gut closed, since they are proteins and I assume would simply be digested...but this is not my area of expertise so I could very well be wrong.

Yup. I've wondered the same thing.
However when people comment that it's great I'm still nursing DS (he's 16 months) because it's good for his immune system, I don't argue with them! I figure that good nutrition, being hydrated and snuggling with mama can only help him stay well.

[Materfamilias]

There is an article on this topic in the current New Beginnings mag that LLL puts out. The article refers to this source:
Hanson, L. Immunobiology of Human Milk: How Breastfeeding Protects Babies. Pharmasoft Publishing, 2004.
The article refers to immunological benefits, but also "thousands of different components that support the immune system in some way...defending against a particular pathogen [or they have] a broader function. "
Reference is made to the distinctive mix of oligosaccharides found in individual mother's milk that "can block infection by preventing a particular strain of bacteria from sticking to the gut wall." Apparently this can occur even if the mother has not been exposed to the bacteria herself.
The article also discusses SlgA antibodies that work in the baby's gut, nose, and mouth.
A milk protein called lactoferrin works as an anti-inflammatory--what cures the pinkeye, I guess--and is peculiar to humans.
Finally, the article does say that, while babies' immune systems need more protection when they are under one year old, their immune system does not fully mature until they are six years old.
There's more, but I've blathered long enough.

[paulamc]

Originally Posted by Materfamilias

The article also discusses SlgA antibodies that work in the baby's gut, nose, and mouth.

Thanks for this post! I've been following this thread with interest and until reading this, had completely forgotten about the above point. I'm no expert on the subject at all, but in my cursory research on the immunological benefits of breastfeeding prior to my DS's birth, my takeaway was that there are two main ways in which breast milk protects against illness. I'm sure it's more complex than just "two ways" but in any case, one of the ways I recall reading about was that it creates a sort of protective barrier coating of the nose and throat that disables / stops pathogens from entering the system. It seems like this should work however old the child, right?

ETA: WHOOPS - I had not read the recent posts, and see now that someone else mentioned this point from Sears. That's probably where I originally read it as well.

[CheriK]

It's a lot more complex than simply gut closure, as immune contact occurs in the gut and other mucosa (such as the respiratory tract) life-long, with most immune cell types (hah - looked it up - IgA producing cells, T and B lymphocytes) located in the gut mucosa. According to Lars Hanson's book Immunobiology of Human Milk, "when fully developed, 70-80% of the whole immune system is located in the intestinal mucosa." In the child, these would still have contact with maternal immune cells, which can modulate immune response, introduce antibodies to pathogens in the environment, and inhibit inflammation (which can affect food and environmental allergic response). And in the maternal gut, some of these cells migrate to the secretory cells in the breast, so the nursling receives immune support based on the pathogenic expose of Mom's gut. These substances from mom aren't digested by the infant gut. They remain intact to do their jobs. Isn't this why most pediatric organizations world-wide (ignore the backward AAP) suggest that breastfeeding continue until at least 2, as the immune system is still developing?

You might want to explore Dr. Stephen Buescher's work on the anti-infectious and anti-inflammatory properties of human milk. LLLI has several podcasts of his presentations (http://www.llli.org/podcasts.html). I've heard him speak twice, and he is a truly amazing speaker. He is so excited and passionate about his work. Like much of what others have posted, however, the research he cites looks at infants, not older children. His basic presentation premise is that breastmilk is a "sophisticated and integrated infant support system", and oh, yeah, it also provides food (but that's secondary, as much of what goes into the infant is NOT in fact digested by the baby).

Most of the research, especially research done prior to the last handful of years, groups breastfeeding over 12 months (sometimes younger) into one category, so unless you can get your hands on original data, it's pretty much impossible to see any changes in immune function for what we would consider "extended" breastfeeding. And a lot of studies, even now, aren't particular about amount of breastfeeding, so they may be grouping children who receive "any" breastmilk with those who are exclusively breastfed. It's frustrating for those of us who want data, but I can understand it. There's not too much research money in this area, and we know that breastfeeding in infancy give the greatest response, so the research will focus on this area.

Some info on immune factors in milk (mostly taken from another old article, Chandra RK. “Prospective studies of the effect of breastfeeding on incidence of infection and allergy”. Acta Paediatr. Scand. 1979; 68:691-694; as well as Lars Hanson's book.)
Immune factors: It used to be thought that only colostrum had a high level of immune factors, which, in the course of lactation, diminished and after six months were only of minimal importance. Today we know that the level of immunoglobulins actually rises after six months, apparently as a reaction to the diminishing milk volume. At 20 months the IgA and IgG levels are about the same as the levels measured after two weeks of lactation. When we think about it, it makes good sense that some protective factors increase at this age because children from about six months on are very mobile; they go everywhere, put everything in their mouths.
•Lysozyme, a non-specific anti-microbial factor which increases in mother’s milk and in some cases by 12 months has reached the same level as in colostrum. The research indicates that it continues to increase until the child is about 25 months old and only then does the level begin to fall. One ml of mother’s milk has about 4000 living cells (mostly lymphocytes and macrophages) which hinder the growth of bacteria, viruses, fungi and parasites.
•Bifidus factor in mother’s milk continues to promote the growth of the lactobacillus bifidus in the child’s intestinal tract which inhibit replication of shigella, salmonella and some E. coli (Riordan J and Auerbach, K 1993).
•Interferon, an anti-viral factor, and lactoferrin which prevents the growth of E. coli, salmonella and Candida albicans by binding with iron, are also in mother’s milk. It has been shown that lactoferrin levels increase continuously.

[IAMommy]

I don't have anything to add, but this is all very interesting. I wish I would have seen this thread before Thanksgiving and I would have had more ammo for the relative who said that the fact that I am pregnant and have no plans to wean my 18 month old toddler is "weird." All I had was the WHO recommendations, which she countered by saying that we have other sources of nutrition, this isn't a developing country. Sigh.

My personal anecdotal evidence of EBF being good for toddler's immunity too, is that DS has been sick three times in his life. Just colds, never an ear infection. He touches everything (including the toilet) and his fingers go right into his mouth. Eight to 10 colds a year my foot.