Breastfeeding nutures and protects babies and their mums in many ways, but Dr Karl discovers breast milk still has plenty of secrets to spill.

Breastfeeding nutures and protects babies in many ways that we still don’t understand (Source: Elena_P/iStockphoto)

The year 2012 is the 50th anniversary of the very first silicon breast implant. It was performed in Houston Texas, and Timmie Jean Lindsey still has the implants. Even though they have ruptured, she doesn’t want them removed. But aside from how a breast looks, one of its main functions is to feed the newborn child.

As you would expect, all mammals (not just humans) have mammary glands. In the human, boys and girls have identical mammary glands until puberty, when the hormones make them change shape.

Humans are the only mammal in which the females develop breasts at puberty, and then keep them for the rest of their lives regardless of their reproductive or lactating capability.

Looking at non-human mammals, the female Rhesus macaque monkes produce different milk for their sons and daughters.

The boy monkeys receive a more concentrated milk, so they spend less time with their mothers, and more time playing and exploring. These skills will be useful when they leave the group.

The Rhesus macaque monkey mothers make a milk for their daughters that is less concentrated, but still provides the same nutrition because they produce more of it. As a result, the daughters have to hang around their mothers for more frequent feedings and this helps consolidate their matrilineal society.

Getting back to humans, there’s an advantage to breastfeeding for the mother. Back in the Renaissance, the doctor Bernadino Ramazzini was the first to note that breast cancer occurred more frequently in nuns than other women.

Today we know that if a woman delivers and breast feeds her first child before she is 20, she has about half the risk of breast cancer than either a mother who had her first child after the age of 30, or a woman who has never had a child.

But breastfeeding has another effect upon the mother. It relates to that old saying in North America: “Never get between a mumma bear and her cub”.

Bears will defend their young ferociously as will macaque monkeys, rats and mice, prairie voles, hamsters, lionesses, deer, cats, rabbits, squirrels and even sheep. In mammals this is called ‘lactation aggression’ or ‘maternal defence’.

And according to research by Dr Jennifer Hahn-Holbrook and colleagues, human mothers can now be added to the list of lactating aggressors.

She found that breastfeeding mothers were about twice as aggressive than either formula-feeding mothers or women who had never been pregnant. And just like non-human mammal mothers, they were aggressive with a cold calm. Their blood pressure rose less (under the same aggression-inducing circumstances) as it did for the formula-feeding mothers.

Dr Hann-Holbrook speculates that in the ancestral past, this aggression may have deterred predators. The breastfeeding mothers wouldn’t place themselves or the infants in harm’s way, but if attacked would defend themselves vigorously and aggressively.

Even today, breast milk is still surprising us. The molecular biologists, biochemists and geneticists who attended the 15th meeting of the International Society For Research In Human Milk And Lactation in Lima, Peru, had plenty of bombshells.

For example, I always thought that breast milk was served up to the baby sterile with no bacteria in it. But it turns out that up to 600 different species of bacteria can be cultured from one single sample of breast milk. It seems that breast milk is similar to a complex cultured yoghurt, in the sense that many different species of bacteria are doing stuff we still don’t understand.

Another major surprise is about the nutrients in breast milk. Basically breast milk contains fats (about 4 per cent), proteins, carbohydrates and a whole bunch of other stuff. The other stuff includes vitamins A, C, E and K, as well as some essential minerals. Besides the well-known lactose (a carbohydrate), there are also some mysterious oligosaccharides. (Oligosaccharides are also carbohydrates, and are made of short chains of various sugars joined together). On a percentage basis, there is roughly as much oligosaccharide as there is protein in breast milk. Not all mothers make the same set of oligosaccharides, but we do know that they tend to vary roughly following the mother’s blood group.

Now here is a very weird thing. The baby cannot digest these oligosaccharides so why are they there?

Perhaps they are there to feed the rapidly changing populations of bacteria in the baby’s gut. At this stage, we simply don’t know. What we do know is that they won’t put the babies off the breast milk.

Tags: breast-feeding, animal-behaviour, breastfeeding

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Published 10 July 2012

2012 Karl S. Kruszelnicki Pty Ltd

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11 Jul 2012 12:01:27am

Dr Karl, there are also embryonic like stem cells in breastmilk. Cells which can be manipulated to form many different differentiated cells. These are being explored by Australian scientists in Perth, with Dr Peter Hartmann.
Breastmilk contains much we don’t even know about, but babies love it!

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11 Jul 2012 11:56:54am

We are not Rhesus monkeys so drawing a parallel with humans is seriously flawed.

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11 Jul 2012 3:04:31pm

Robert: perhaps you need to look beyond this and see the wonders of breastmilk, which is what this article appears intended for.

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17 Jul 2012 10:39:22am

Duly noted, kg.

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11 Jul 2012 3:19:27pm

Robert, I don’t see that Dr Karl has drawn any parallels between humans and Rhesus monkeys. It’s more of a perpendicular…

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12 Jul 2012 9:23:03pm

Robert, Dr Karl is not drawing a parallel between humans and Rhesus monkeys. He was merely highlighting how another group of mammals use breastfeeding.

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17 Jul 2012 10:38:59am

Agreed, Linda J!

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17 Jul 2012 10:38:00am

There is a difference between comparatives and parallels. This is a transparent attempt to dismiss the evidence. Why not try instead to further investigate the value of natural functions, such as human breastfeeding studies?
A friendly correction.

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11 Jul 2012 12:17:10pm

Dear Dr Karl,

Thanks for writing an informative & enjoyable article about the amazing ‘surprise value’ of breast milk.

I really love the amazing beauty & detail of the female breast….physical, emotional, sexual, psychological, nutrition, health.

In regard to the nutrition of breast milk, I remember reading an article quite some time ago that discussed two fatty acids that occur naturally in breast milk – Docosahexaenoic acid (DHA) and Arachidonic acid (AA) & that these fatty acids seem to make a difference to neural development in terms of memory, problem solving & language development skills.

I clicked on the photo of the breastfeeding mum that accompanies your article…it’s a really beautiful picture of blissful peace.

Thanks again Dr Karl for your article on Breast milk.

Kind regards,

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11 Jul 2012 12:41:27pm

hahaha. Robert,time for a reread! the parallel drawn was that we are both mammals, who therefore lactate. The article was about amazing breastmilk, and the rhesus monkeys breastmilk is just as amazing as human breastmilk! I love the animal comparison. Between different mammals some are cache mammals and some are carry and the milk of each species is differentiated to provide a different balance of fat to either sustain for longer periods between feeding or to be quickly digested in animals that are carried and have constant access to small and often feeding.


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11 Jul 2012 8:04:55pm

Interesting comments about bacteria. It’s not a surprise to me at all. The argument for the purported benefits of raw milk in general involves related ideas, even if they are currently controversial.

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12 Jul 2012 11:38:24am

Dr Karl, I think you have somewhat undersold the advantages of breast milk. There are also the water soluble vitamins, plus lactoferrin, which we now know has anti-cancer properties, plus insulin, IGF1, EGF and many other growth factors that are very important for maturation of the infants intestine. Manh of these proteins are also absorbed intact by the juvenile gut, which is a good reason for the developing child to have human mmilk rather than the antigenically foreign milk from other species.

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12 Jul 2012 8:50:59pm

So does this mean that we needn’t be so precious about sterilising bottles, pumps and teats?

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14 Jul 2012 1:59:18pm

Hi- yes that’s right. Breastmilk can be fed to a baby in a bottle that does not need to be sterilized but washed with very hot soapy water and rinsed with very hot water. This was explained to me by an Australian breastfeeding association counsellor. O and pumps etc too are fine to only be washed by soapy water , I think basically the good bacteria also acts as an antibacterial surface protector.

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15 Jul 2012 4:23:45pm

Yes Jess, you don’t have to sterilise as much when breastfeeding verses bottle feeding. It’s still important to maintain hygiene but as long as you are exposed to the same bugs as the breastfeeding bub your body will make any antibodies they need and into the next feed they will go. My eldest was suspected to have measles (yes before everyone starts he was immunised but not all immunisations are 100% effective) when his younger brother was 6 weeks old. Both milk and blood samples where taken from me and the milk was found to have measles antibodies giving him the protection before he was immunised! Liquid gold is right!!

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17 Jul 2012 8:28:49am

wonderful….nature …

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12 Jul 2012 11:01:07pm

Thanks Dr Karl for the further education on the wonders of breastfeeding. It is so important to keep educating our culture on this topic. As a mother of two young ones, I see there is still such a gap in the knowledge of many people.

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25 Jul 2012 4:43:45pm

Compleatly agree! I am the odd one out in my group of friends… still breastfeeding at 6 mths. It seems to be more normal now to formula feed then breast feed. So proud of myself for pushing through those difficult first months it was definatly worth it in the long run for me and my little boy.

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13 Jul 2012 1:16:35am

Liquid gold!!

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17 Jul 2012 10:40:28am

Chrissy: heartily agree!

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17 Jul 2012 9:56:21am

Absolutely fascinating! Thanks for posting this article up, really enjoyed reading it.

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17 Jul 2012 10:43:53am

Thank you, Dr Karl, for posting this intriguing and informative article on recent findings re: the value of breastfeeding for humans!
So glad that many are returning to this vital component of propagating our species…

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17 Jul 2012 12:23:05pm

Certainly some fascinating research still to be done into human lactation! My two favourite things about breastmilk are the appetite-promoting cannabinoids (that help encourage my fussy and distractible 2 year old to eat a full meal) and the feel-good hormones that help both of us deal with some of the more testing aspects of the terrible twos!

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18 Jul 2012 10:59:02am

My favorite is the sleep hormone! Puts both bub and mum to sleep, especially at night when/if you’re worrying.

There are also cancer killing agents in there.

Breastmilk actually sterilizes, if you add bacteria in there, they die rather than make the milk go off. It kills the bacteria that cause tooth decay.

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26 Jul 2012 7:53:53pm

Breastmilk also works well as a cure for conjunctivitis. It is a natural antibiotic. It fixed my baby’s eyes a few times.

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18 Jul 2012 9:46:42am

I’ll be taking this to La Leche League tonight. Thanks, this was great!!

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18 Jul 2012 10:58:32am

Thanks, excellent and interesting article. Am pregnant with my second child and am so looking forward to the breasfeeding relationship again… beautiful silent hours of the early morning just baby and I sharing feel-good hormones and tender togetherness. Breastmilk is magical indeed.

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18 Jul 2012 10:21:28pm

A beautiful article! Thank you for sharing! And some beautiful comments sharing even more! The miracle that is breast milk! So thankful to have educated myself and to have chosen to nurse my son! And so very thankful to see more and more knowlege being brought to the foreground for the public!

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19 Jul 2012 8:51:22am

i am a little confused about the whole ‘ being agressive ‘ thing…i really dont see myself as an agressive person at all! lol! then again ive never been in a situation where my children or myself are being threatened. any more points on this? great article though! im breastfeeding my one month old as i read/comment on this ๐Ÿ™‚ i am now a mother of two, very glad to be breastfeeding again ๐Ÿ™‚

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