Technical question re BF and antibodies

[ChubbyStuckForAFestiveNameBurd]

In cattle and sheep (bear with me!) the gut of a newborn is only able to absorb immunoglobulins for the first few hours of life - for a calf we'd say 2 litres of colostrum within 6 hours of birth is a minimum to avoid illness. After the first 8 hours the gut becomes impermeable to the Ig proteins and they are simply digested like any other foodstuff.

I often hear reference to the beneficial effects of antibodies in BM for older babies (ie not newborns) - how does that work then?

[lljkk]

I'm not pretending to be an expert but the question intrigued me so I tried to come up with an answer. You might have to wait until after New Year for a clued-up MN expert to see this and reply.

I think this is a common myth for breastfed toddlers, that there are no immunological benefits. Keep in mind we are not cows, to start with.

Had a quick look on Internet and the sources I've found on the Internet say 24 hours for calves, puppies, kittens or piglets and absorption of colostrum immunoglobins (not 8 hrs).

This page talks about early milk immunoglobin absorption for different mammals, making it clear that ruminants are quite different from say, rats (20 days of absorption) or people. Also, there are different concentrations of various types of immunoglobins in different types of mammalian milk, and some of these can beneficial just via the mouth or stomach membranes, alone. IgA and IgG in breast milk counteract bacteria in the mouth and lactoferrin actually kills streptococcus mutans, regardless of the age of recipient (see ref).

Another thing, ruminants start eating grass typically by 2 weeks of age, whereas baby people need to be something like 10x older to be ready for non-milk food, so we would expect human milk to be more specialised and complete.... Plus people live at such high densities and intense social interaction that we have probably evolved quite differently in terms of what our immune systems need to cope with.

I'm also guessing that the types of antibody molecules in mature milk are different from colostrum (not as many, but smaller molecules). Also, that they are in there at all may mean something -- they wouldn't be there if they didn't tend to benefit the offspring. Most importantly, we know that the longer they're breastfed, babies and toddlers get the fewer colds, and they generally get milder versions of whatever illnesses mother might have (like a cold), so that's epidmeological evidence that at least some antibodies get thru somehow long after the newborn period.

[ChubbyStuckForAFestiveNameBurd]

Wow, I was expecting this one to spend the rest of its days collecting cyberdust in 'unanswered threads', so thank you! I feel really ashamed now though. I should have researched it myself [lazy bint emoticon] - thank you!

I did wonder if it was a ruminant thing. There is still absorption up to 24hrs, I worded that badly totally wrong but I was taught (a few years ago now but not decades ) that optimal colostrum absorption was within 6 hours and beyond 8 hours it was of negligible benefit (other than the obvious nutritional density). Of course the average healthy calf would have a full feed well before 6 hours had passed. I also suspected there might be local effects, but I hadn't thought about lactoferrin.

If necessary, I can now defend my plans for so-called 'extended' BFing to my sceptical colleagues with science. Cheers!

[LyraSilvertinsel]

Babies and calves are not the same.

[SallyInYorkshire]

I agree it's an interesting question although I'm no expert!! I have studied some immunology in my time though so here goes...

One of the problems is that it is difficult to do controlled studies and probably unethical to do lots of blood sampling on healthy babies out of scientific interest just to see what they're absorbing!

But even if none of the IgA was absorbed by the baby, the gut is a major potential portal for entry of infections for little babies and even just having breastmilk IgA antibodies hanging around inside the gut, without being absorbed, is likely to have some protective effect.

From a quick google search it seems to me that there IS a lasting direct immune benefit of breastfeeding up to at least 3 months; indirect benefits may persist for many years. But the immunological mechanisms of even the direct benefits are very complex, not completely understood and not simply due to passive transfer of antibodies.

www.blackwell-synergy.com/doi/abs/10.1111/j.1651-2227.1999.tb01299.x

www.blackw ell-synergy.com/doi/abs/10.1111/j.1399-3038.1995.tb00254.x

www.sciencedirect.com/science?_ ob=ArticleURL&udi=B6TD4-48M829N-2&user=10&rdoc=1&fmt=&orig=search&sort=d&view=c&acct=C0000502 21&version=1&urlVersion=0&userid=10&md5=861983af4714721d5de7f3bce41199c9

content.karger .com/ProdukteDB/produkte.asp?Aktion=ShowAbstract&ArtikelNr=14018&Ausgabe=225275&ProduktNr=224215

[LyraSilvertinsel]

lljkk's explanation was a little fuller than mine.

[lazyemma]

Yes, you can't compare babies and calves. Babies, unlike the young of other mammals, are born with passive immunity, and have a large supply of maternal antibodies that were transferred to them via the placenta when they were in utero. Calves etc do not, and therefore need to get all their passive immunity them from colostrum: for the first day or so after birth, antibody molecules can pass through the gut wall. If a newborn calf can't get to its mother's milk (or that of another cow) within the first day, it will die. The same is demonstrably not true of babies.

Antibodies in human breast milk are thought not to pass through the gut wall, except in the very tiniest amounts. Instead they work locally within the gut. See here:

www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TD4-48KNS52-C&_user=10&_rdoc=1&_fmt=&_orig=searc h&sort=d&view=c&acct=C000050221&version=1&urlVersion=0&_userid=10&md5=0d286b44e05374dfe258d40542 24f2e0