Most contemporary breastfeeding research is deeply suspect because researchers start with the conclusions — breastfeeding must be best! — and work backward to support it.
As one after another of claimed benefits of breastfeeding have melted away when studies are corrected for maternal education and socio-economic status, breastfeeding researchers have become ever more creative in fabricating fanciful new “benefits.” The latest fad is to claim epigenetic benefits of breastfeeding.
There are 5 reasons to ignore epigenetic claims about breastfeeding, but before we review them some background is in order.
As benefits have melted away when studies are corrected for socio-economic status, breastfeeding researchers have become ever more creative in fabricating fanciful new “benefits.”
What is epigenetics?
Epigenetics refers to mechanisms of gene regulation that determine the state of a cell and that are heritable through cell divisions but that do not involve changes in DNA sequence… It is often more specifically used to refer to chemical modifications (such as methylation or acetylation) of DNA or of the histone proteins associated with it in chromatin. These epigenetic marks can affect gene expression and can be stably inherited from one cell to another (i.e., through mitotic cell division).
The impact of epigenetics was discovered long before anyone understood the mechanisms of genetics, let alone epigenetics. Researchers noted that famine in Northern Sweden in the mid 1800’s seem to affect the health of their grandchildren decades later. In a subsequent observation, children who had survived famine during WW II seem to suffer more cardiovascular disease later in life.
[Lars Olav] Bygren had a long running interest in the lifelong effects of nutrition, and particularly of starvation…
Bygren realized that Överkalix, where he was born, would make for a perfect study. Not only were there centuries worth of birth, death, and agricultural records, but the people living in the remote terrain of Överkalix had remained genetically isolated for centuries.
What did he find?
Among the 1905 birth cohort, those who were grandsons of Överkalix boys who had experienced a “feast” season when they were just pre-puberty—a time when sperm cells are maturing—died on average six years earlier than the grandsons of Överkalix boys who had been exposed to a famine season during the same pre-puberty window, and often of diabetes… It appeared that Överkalix grandfathers were somehow passing down brief but important childhood experiences to their grandsons…
Modifications in response to famine — not of DNA itself but of chemical tags on DNA that control expression of genes — could be inherited.
Breastfeeding researchers promptly seized on that fact to make new claims:
The notion of epigenetic effects of breastfeeding seems to be widely held, and a Google search (January 23, 2017) using the search terms “epigenetics breastfeeding” resulted in approximately 111,000 hits…
At the moment there is no evidence that breastfeeding has any causal epigenetic benefits and considerable reason to ignore such claims.
1. Even with established epigenetic effects, the impact is paradoxical:
For instance, why is it that the amount of food available to a paternal grandfather seems to affect the mortality risk ratio of his grandsons but not his granddaughters? Or why is it that the food supply of a paternal grandmother is only associated with the mortality risk ratio of her granddaughters? Pressing even further, why would a reduced risk of cardiovascular death be linked to a mother’s good food supply but also to a father’s poor food supply? Right now, we just don’t know the answers to these and similarly complex epigenetic questions.
2. To date, most epigenetic associations involve environment, not exposure to specific substances.
An environment of famine or plenty has been shown to have epigenetic effects, but single foods have not. It is entirely possible that any epigenetic impact of breastfeeding has more to do with the amount of breastmilk (or formula) available than with the substance itself.
3. Although we don’t know for sure, it is assumed that epigenetic effects are adaptive.
The epigenetic impact of famine is different than the epigenetic impact of plenty because famine requires different adaptations to maximize survival than plenty requires. Famine is a recurring theme in human history; it makes sense that humans would have developed adaptive strategies to improve survival.
In contrast, whether or not a specific food (e.g. wheat, honey, deer meat) is available does not seem to impact survival so there is no reason to “adapt” to it. Unless and until we can show that specific foods matter, there is no reason to believe one — including breastmilk — has any epigenetic “benefit” over any other.
Moreover, until recently there has been no safe substitute for breastfeeding. Therefore it is difficult to imagine why breastmilk would have induced epigenetic adapatations.
4. Socio-economic status almost certainly has an epigenetic impact.
Differences in socio-economic status creates differences in environment. Children growing up in poverty have a completely different set of biological challenges than those growing up with wealth. Impoverished children may experience a longterm evironment of food scarcity, contaminated water, inadequate heating, and limited or no access to treatment for common health problems. They may develop epigenetic adaptations to meet those challenges.
Socio-economic status is already a confounding factor in breastfeeding research. In industrialized countries breastfeeding is closely tied to higher economic status. Almost all the health “benefits” of breastfeeding are benefits of wealth. Similarly, any epigenetic “benefits” of breastfeeding may actually be epigenetic benefits of wealth.
5. The prenatal environment may lead to epigenetic changes that modulate infant response to the postnatal environment.
Newborn babies aren’t new. They’ve been growing and developing for 9 months before birth in an environment determined in part by their mother’s environmental exposures. It is highly plausible that starvation, pollution, environmental exposures such as those to tobacco and alcohol and maternal illness could have epigenetic effects on the developing fetus. These pre-existing epigenetic changes may modify the impact of breastfeeding on babies. At the moment these cannot be teased apart from epigenetic effects of poverty or theoretical epigenetic effects of breastfeeding.
The claim that breastfeeding has epigenetic benefits — in the absence of evidence of causation of any kind — is a sign of desperation among breastfeeding researchers. As previously claimed benefits evaporate when exposed to greater scientific scrutiny, breastfeeding researchers have had to plumb deeper for new “benefits.” But the bottom line remains the same:
Breastmilk is milk, not magic, no matter how vehemently breastfeeding researchers insist otherwise.
