Lactivists are constantly making claims about breastfeeding that aren’t supported by the scientific evidence.
I’ve written extensively about debunked claims that breastfeeding prevents obesity, diabetes, high blood pressure and a host of other chronic conditions. Those erroneous claims can be traced to the confounding variables found in most breastfeeding studies. Women who breastfeed are wealthier, more educated and have greater access to healthcare. What appears to be a benefit of breastfeeding, actually turns out to be a benefit of higher socio-economic status.
As those claims are being rolled back, lactivists have advanced a new, rather extraordinary claim: that mothers and babies communicate through breastmilk.
[pullquote align=”right” color=”#e2d3e1″]There are far simpler explanations for the presence of bioactive compounds in breastmilk than spit backwash.[/pullquote]
In The More I Learn About Breast Milk, the More Amazed I Am, Angela Garbes writes:
According to Hinde, [Katie Hinde, a biologist and associate professor at the Center for Evolution and Medicine at the School of Human Evolution & Social Change at Arizona State University] … If the mammary gland receptors detect the presence of pathogens, they compel the mother’s body to produce antibodies to fight it, and those antibodies travel through breast milk back into the baby’s body, where they target the infection.
But that’s not all:
Even before babies have any concept of time, breast milk helps them understand certain hours from other hours, night from day.
“Milk is so incredibly dynamic,” says Hinde. “There are hormones in breast milk, and they reflect the hormones in the mother’s circulation. The ones that help facilitate sleep or waking up are present in your milk. And day milk is going to have a completely different hormonal milieu than night milk.”
Or as Hinde said to me in a Twitter conversation:
… [T]his is one example of the complex biofeedback system of breastfeeding that many people don’t know & should.
Actually, it’s yet another example of the white hat bias toward breastmilk that leads researchers like Hinde to make claims that far, far outstrip the existing scientific evidence.
What is white hat bias?
‘White hat bias’ (WHB) [is] bias leading to distortion of information in the service of what may be perceived to be righteous ends…
Indeed white hat bias was first described in association with breastfeeding research:
Certain postulated causes have come to be demonized (… formula feeding of infants) and certain postulated palliatives seem to have been sanctified.
Let’s look at the ways that white hat bias has led to outsize claims about the properties of breastmilk.
Breastmilk researchers start with certain fixed, unquestioned assumptions about breastmilk such as:
- Breastmilk is assumed to be an unalloyed “good.”
- Components of breastmilk are assumed to be beneficial.
- The components of breastmilk are assumed to be directed in whole or in part toward the benefit of the baby.
Breastmilk is definitely an excellent way to nourish an infant. But breastmilk, like any biological product, is not perfect. Sure, it’s the product of millions of years of evolution, but evolution can only work with what it has available; it can’t create de novo. For example, it would confer a tremendous survival advantage to have eyes in the back of our heads, yet we don’t have them. Why not? The animal genome by and large is restricted to a body plan with two eyes at the front or sides of the head. Evolution can’t spontaneously generate four eyes from the genes for two eyes. Evolution cannot spontaneously add nutrients to breastmilk simply because they are needed by the baby. They must be available in the mother’s body first.
Not all components of breastmilk are beneficial. Breastmilk is a bodily fluid derived from other bodily fluids. Therefore, it is has components that reflect what is in the maternal bloodstream whether those components are good (antibodies) or bad (viruses, medications, industrial chemicals) for the baby. HIV, the virus that causes AIDS can be found in human breastmilk of mothers infected with HIV and can be passed to the baby. The virus is bad for the baby, but since it was in the fluid used to create breastmilk, it ends up in the breastmilk, and often kills the baby. It is entirely unjustified to assume that the presence of a bioactive compound in breastmilk means that it’s there for a good reason.
Prof. Hinde was irritated with my criticism of her claims and sent a bibliography salad of references to me through Twitter.
At the very best, those reference show correlations between certain conditions and certain components of breastmilk. But correlation is not causation.
There are 9 criteria, known as Hill’s Criteria that can tell us when a correlation shows causation. One of those criteria is “consideration of alternative explanations.” Before claiming that A caused B, you must consider and rule out the more likely possibility that B occurred for a reason entirely independent of A. If you graph consumption of organic food against incidence of autism, you’ll find that as the consumption of organic food has risen over the past decades, the incidence of autism has risen almost in parallel. That does not mean that organic food causes autism.
Hinde and other researchers on breastmilk have noted that when babies are sick, the antibodies content of breastmilk rises. They’ve even proposed an extraordinary mechanism for how the baby communicated to its mother that it was sick. Their theory is known as “spit backwash.” Baby saliva is literally sucked into the breast where the mother’s body senses the pathogen and makes antibodies in response.
But there is another far simpler, far more likely explanation. It’s hard for two people to be much closer than a mother and her feeding infant. If a baby has a cold, for example, the mother can simply BREATHE IN the virus expelled when the baby sneezes and make antibodies to the virus to protect HERSELF from the cold. Those antibodies then end up in the breastmilk incidentally as a result of being in the mother’s bloodstream. If researchers had looked, they would likely have found that the father and siblings were making the same antibodies as the mother, not to transmit them to the baby, but to protect themselves.
Is it possible that the mother made the antibodies as a result of saliva being backwashed into the breast and created them in order to protect the baby? Sure, it’s possible, but you’d need a great deal more evidence to draw that conclusion. You’d need to show that the mother would make the same antibodies even if she hadn’t had oral and nasal exposure to the baby’s secretions. Furthermore, you’d need to show that those antibodies made it into the baby’s bloodstream and are biologically active there. As yet, no one has shown anything of the kind.
How about the claim that breastmilk helps facilitate infant sleep?
Yes, there are sleep promoting compounds in breastmilk produced at night, but that doesn’t mean they are there to help the baby sleep. They may be there simply because the mother is tired. In other words, the presence of these compound is incidental. Is it possible that they induce sleep in the infant? It’s possible but not particularly likely since babies have their own sleep patterns that are, sadly, unrelated to their mothers’ need and desire for sleep.
When I questioned Hinde more closely on these types of claims and presented simpler alternative explanations than spit backwash, she began walking them back:
I agree that there are reasons for maternal antibodies to be protecting the mammary gland & things can be byproducts… but I think you are also confusing the matter of science publications that grapple w/ these complexities… & aspects of the science communicated broadly: the article discusses this as one potential pathway… there is evidence for that… but doesn’t make arguments that it the ONLY pathway or that this is the ONE function of that pathway.
This is a far more nuanced view, but hardly the view that she has been presenting in her interviews and writing for laypeople where she insists that “mammary gland receptors detect the presence of pathogens, they compel the mother’s body to produce antibodies to fight it, and those antibodies travel through breast milk back into the baby’s body, where they target the infection.”
Do mothers and babies communicate through breastmilk? At the moment, that’s wishful thinking abetted by white hat bias. The existing scientific evidence shows that there are antibodies and other bioactive compounds in breastmilk; those studies are small, show only correlations, and are themselves affected by white hat bias.
There are far simpler explanations for the presence of antibodies and other bioactive compounds in breastmilk than spit backwash. They are created by the mother to protect the mother. Any benefit to the baby has yet to be demonstrated.
