In honor of World Breastfeeding Week (yes, yes, I know–it ended yesterday), we need to talk about a widely overlooked aspect of breastfeeding, its recipients!
Nope, I am not talking about our babies. (After all, who could overlook them?) I am talking about their gut bacteria.
Breast milk contains special carbohydrates (called HMOs for Human Milk Oligosaccharides) designed to nourish specific gut bacteria, especially a type known as Bifidobacteria. Bifidobacteria contain genes desiged to metabolize HMOs–implying they have co-evolved with us for a long time.
This process of seeding your baby’s gut begins not with breastfeeding, though, but before birth. During pregnancy, women’s bodies cultivate these bacteria while pruning out others, seemingly in preparation to pass them onto our babies during birth.
Why does this matter? Because some of breastfeedings health benefits may occur through this cultivation of gut bacteria. A healthy balance of gut bacteria in early infancy is believed to help calibrate baby’s immune system development and metabolism, possibly with lifelong effects.
I dig into the latest research on the breastfeeding-gut-health axis in my latest post for BloomLife. Check it out!
Breastfeeding and not losing any weight? The evidence suggests you are not alone.
Breastfeeding melts off the baby weight, right? Or so we are told. Breastfeeding leads to an “earlier return to prepregnancy weight,” according to the American Academy of Pediatrics (AAP).
This is because “breastfeeding burns extra calories, so it can help you lose pregnancy weight faster,” as many popular websites, like WebMd claim.
Sounds pretty clear cut, right?
So when I failed to lose weight while breastfeeding my first child, I was shocked. Weren’t those pregnancy pounds supposed to practically fall off? Why were my pre-pregnancy jeans still relegated to the back of my closet?
Breastfeeding an infant does burn an average of 480 calories a day. So why wasn’t I losing more weight?
But like so many other alleged benefits of breastfeeding, breastfeeding-aided weight loss turns out to be vastly overblown.
In other words, my experience was completely normal. For most well-nourished women, long-term breastfeeding results in only a trivial amount of extra weight loss by 6 months postpartum, usually only of 1-2 lbs.
Breastfeeding lowers your child’s risk of obesity, asthma, and allergies. Or does it? The best available research implies these claims are vastly overstated.
A good friend of mine living in Scotland, who had a baby last year, mentioned to me how disappointed he has been with the U.K. National Health Service’s promotion of breastfeeding. Calling the alleged benefits overstated, he said, is itself an understatement.
I nodded in general agreement, acknowledging that many of the alleged benefits of breastfeeding have only been found in observational studies.
Observational studies on breastfeeding merit skepticism, because they all suffer from the same major problem: breastfed infants on average differ from formula-fed infants not just in how they are fed in infancy, but in practically every other possible way–maternal education, maternal IQ, poverty, neighborhood safety, exposure to environmental toxins, race, and type and quality of childcare. In scientific terms, breastfeeding is confounded, out the wazoo.
We cannot tell which benefits found in an observational study derive from breastfeeding rather than from the myriad other advantages linked with breastfeeding.
(The “good” observational studies attempt to control statistically for the other relative advantages of breastfed infants. Unfortunately, controlling for confounds only works well when (1) all the important potential confounds are known, and (2) when there is a fair amount of overlap between the groups being compared. Neither of which is true when it comes to breastfeeding.)
In an ideal world, we would settle this question by conducting several large randomized controlled trials (RCTs), in which new mothers would be randomly assigned to breastfeed. RCTs are the gold standard in medicine for determining whether a true cause and effect relationship exists. In practice, though, such trials are neither feasible nor ethical.
Fortunately, we have the next best thing: a handful of studies that have cleverly circumvented the problem of confounding. These fall into two categories:
sibling studies, which compare siblings from the same families who were breastfed for different lengths of time, or who were not both breastfed.
a large RCT of a highly successful breastfeeding intervention (PROBIT Trial).
(Is the PROBIT Trial an exception to the no-RCT rule? No. Women in the PROBIT trial were not randomly assigned to breastfed or not; they were randomly assigned to receive a breastfeeding intervention or not.)
After my friend and I spoke about his irritation with the medical organizations like the American Academy of Pediatrics (AAP) and NHS overstating the benefits of breastfeeding, I was dissatisfied with my vague sense that he was right. I wanted to know exactly which benefits had been oversold and exactly which were supported not just by observational studies but by better-designed studies.
The short answer: Nearly all the alleged long-term benefits are likely the result of confounding, not breastfeeding. Better-designed studies find only a handful of real benefits: a reduced chance of severe gastrointestinal infections and a lower risk of eczema during infancy, and perhaps a small boost in childhood IQ.
Alleged Breastfeeding Benefits According to the NHS
According to the NHS, breastfed infants are…
less likely to suffer from vomiting or diarrhea and therefore less likely to go to hospital
less likely to develop type 2 diabetes in later life
less likely to become obese in later life
less likely to suffer from heart disease in later life
less likely to suffer from constipation
less likely to get a chest or ear infection and therefore less likely to go to hospital
less likely to suffer from tooth development problems
more likely to have good communication and speech skills
more likely to have good circulation
less likely to suffer from wind, colic and constipation
less likely to develop eczema or asthma
Sounds pretty impressive, right? Until you set aside the evidence from observational studies…
How risky is bedsharing with your child? And if you choose to bedshare, how can you do so as safely as possible?
My second baby slept in bed with me, all night, every night, from the time we took her home from the hospital until she was 3 months old. At first, I was almost too terrified to fall asleep, for fear that I would roll over and suffocate her.
After all, nearly all major medical organizations warn against bedsharing, on the grounds that it increases the chances of Sudden Infant Death Syndrome (SIDS).
“The safest place for your baby to sleep is in the room where you sleep, but not in your bed. Place the baby’s crib or bassinet near your bed (within arm’s reach). This makes it easier to breastfeed and to bond with your baby,” according the The American Academy of Pediatrics.
Statements like these sound definitive. But, in fact, considerable scientific controversy surrounds the role of bedsharing in SIDS.
A few weeks ago, I was all set to write about the vitamin D needs of pregnant and nursing women. Increased sunscreen use and less time spent outdoors means that few women can meet their vitamin D needs through sunlight exposure alone. As a result, many pregnant women are insufficient in the vitamin.
The medical community is clearly concerned about women’s low levels of vitamin D: The American Pregnancy Association recently raised their recommended vitamin D intake for pregnant and nursing women from 400 IU to 4000 IU, a tenfold increase. The change was precipitated by a recent randomized control trial, in which supplementation with 4,000 IUs a day was shown to be safe and highly effective at reducing vitamin D deficiency among pregnant women.
I only wish these changes had come sooner.
I say this because last weekend, my daughter Sydney, who turned two this month, was diagnosed with Type 1 Diabetes–a disease that may be staved off, in part, by high levels of vitamin D during infancy.
In 2000, the AAP advised delaying introduction of peanuts and tree nuts until age 3. But new research finds delaying exposure considerably boosts the chances of a peanut allergy.
By now, you’ve probably heard about the recent study, which showed that early consumption of peanuts lowers the risk of peanut allergy by as much as 86%.
The study, led by Gideon Lack of King’s College, London, and published in the New England Journal of Medicine in February, is the first randomized clinical trial conducted on preventing peanut allergy in children. Widely hailed as a game changer, the study’s findings are already affecting the advice given to parents.
Just last week my friend’s pediatrician counseled her to “stir a little peanut butter” into her 6-month-old’s rice cereal. She barely managed to avoid gaping at him in astonishment. Just two years earlier, with her first child, he had told her to avoid introducing peanuts for the first year.
After decades of conflicting advice and vague admonitions, parents may wonder whether such a dramatic change is actually warranted. Is the evidence any better now than it was ten years ago? And if the guidelines were so mistaken before, why have confidence in them now?
And, perhaps the biggest outstanding question of all: what, if anything, does this study mean for when to introduce other highly allergenic foods, like fish, tree nuts, or eggs?
In 2005, the American Academy of Pediatrics (AAP) changed their recommendations from gradually introducing solids between 4 and 6 months of age to exclusively breastfeeding for “about the first 6 months of life. For the first 6 months “your baby”, they assert, “needs no additional foods (except Vitamin D) or fluids unless medically indicated.”
You might think that these recommendations were updated because of a new evidence showing substantial benefits for the baby of delaying the introduction of solids.
But, nope, this is not the case. Instead, these changes were motivated by studies showing an absence of harm to the baby and someminorpotential benefits for the mother.
The World Health Organization was the first major medical organizations to recommend exclusive breastfeeding for 6 months, for reasons they outline in a 2002 research review (updated in 2007):
No evidence exclusive breastfeeding for 6 months results in poor growth
No apparent increase in the risk of allergies*
A longer period of lactation-induced infertility, about an extra month on average
Greater postpartum weight loss between 4-6 months, about a pound on average
Lower risk of illness for the first six months, and possibly throughout the first year
When weighing the pros and cons of exclusive breastfeeding for 6 months, the social and environmental context matters. The WHO crafted its guidelines to maximize health outcomes in both developing and developed nations. But benefits that have a large public health impact in the developing world, where access to basic medical care, birth control, clean water, and nutritious food is limited and inconsistent, can have little or no impact in the developed world.
Benefits of Exclusive Breastfeeding for Six Months
For mothers living in the developed world, the benefits of exclusive breastfeeding for 6 months are small, arguably negligible.
We have been blessed with access to birth control, so lactation-induced infertility is not a critical means of pregnancy prevention and birth spacing.
And, when it comes to weight loss, although almost every mother I know would gladly shed an extra pound or 2 of baby weight, the benefit is really small, just an extra a pound on average. Surely there are other activities that do not require 8-hours a day, round-the-clock efforts that would be just as effective forms of weight loss.
Certainly neither of these two benefits warrant the stress placed on introducing solids “at the right time.”
Of the reasons given by the WHO, the only truly persuasive one is a reduced risk of illness for the baby during its first 6 to 12 months of life. Here again, though, there are important differences between the developing and the developed world.
In the developing world, exclusive breastfeeding for 6 months is literally life saving. Within the 42 nations with the highest child mortality rates, widespread adoption of exclusive breastfeeding for 6 months would prevent an estimated 13% of the deaths of children under the age of 5. This is a larger percentage than would be saved with improved access to antimalarial medication or antibiotics.
Within the developed world, the picture is more nuanced. Here, completely weaning from breast milk before 6 months, or introducing solids before 4 months, or introducing formula before 6 months substantially increases the risk ear infections, diarrhea, pneumonia, and bronchitis.
But gradually introducing solids between 4 to 6 months while continuing to breastfeed does not. Studies that compare the outcomes of infants who were exclusively breastfed until 6 months (EBF or exclusively breastfed) with those who were exclusively breastfed for at least 4 months and then partially breastfed thereafter (MBF or mostly breastfed) find that 6 months of exclusive breastfeeding neither harms nor benefits growth and development.
The only apparent benefit of delaying until 6 months was a 25-50% lower risk of diarrhea in the first year of life. The effects on ear infections, pneumonia, and bronchitis were unclear: A couple of observational studies found a lower risk, but the majority of studies, including the only two randomized controlled trials, found no effect. And longitudinal study conducted in Belarus found no differences in weight, height, BMI, asthma, allergies, or other illnesses by age 6.
“Exclusive breastfeeding for six months does not seem to confer any long-term (at least to early school age) protection against obesity or allergic disease, nor any benefits in cognitive ability or behaviour, compared with exclusive breastfeeding for three to four months with continued partial breastfeeding to six months.” – Kramer & Kakuma, 2012
Costs of Exclusive Breastfeeding
Lower Iron Status. EBF infants tend to have lower iron levels than mixed fed or formula-fed infants. Two randomized controlled trials, one conducted in Honduras and the other in Iceland, found significantly higher iron levels among MBF than EBF infants. Reassuringly, at 6 months of age, iron levels in both groups remained within the normal range, and the EBF infants were not more likely to be iron deficient or to develop anemia.
Still, iron needs rise sharply in the second half of the first year when newborn iron stores have been depleted, and lower iron status in the first six months could place EBF babies at higher risk of iron deficiency as they age. This is why the CDC considers “breastfed babies who after age 6 months are not being given plain, iron-fortified cereals or another good source of iron from other foods” to be at high risk for iron deficiency and anemia.
Increased Risk of Food Allergies. On this point, the advice given to parents has seesawed from it is best to delay solid foods, especially highly allergenic ones, to it is best to introduce these foods early, between 4 to 6 months. This is because the evidence behind the advice is of poor quality and inconsistent. A handful of observational studies find that early introduction increases the risk of allergies. A comparable number find that late introduction increases the risk. And not all of the studies find when solids are introduced matters at all.
Some researchers to speculate that there is something of a sweet spot in infancy, between 4-6 months of age, when introducing solids lowers the risk of allergies. This protective effect may be strongest for peanuts and cooked whole eggs. But until proper clinical trials have been done, it seems wise not to make too much of these findings. (UPDATE: A randomized controlled trial has now shown that introducing peanuts before 1 year of age lowers the risk of a peanut allergy substantially. More on this study here.)
Like so many parenting decisions, the actual evidence suggests that we can all relax a bit. For those of us lucky enough to live in the developed world, introducing a small amount of solids between 4 to 6 months is unlikely to harm our babies, and equally unlikely to benefit them.
That said, when giving your baby solids before 6 months, it makes sense to provide small amounts. The immune benefits of breast milk are dose-dependent: the more milk the baby takes in, the greater the protection from illness. This is why solids during the first year should not be used to replace but to supplement breastfeeding. And when introducing solids, especially to exclusively breastfed babies, it makes sense to emphasize iron rich foods like broccoli, meat, eggs, fish, and fortified cereals.
Here is most sensible statement I found on the 6-month rule, from a review article in The BMJ, the flagship journal of the British Medical Association:
“From a biological perspective, the point when breast milk ceases to be an adequate sole source of nutrition would not be expected to be fixed, but to vary according to the infant’s size, activity, growth rate, and sex, and the quality and volume of the breast milk supply.” – Fewtrell, Booth, & Lucas, 2010
When did you first introduce solids? Did the risk of allergies or infections play a role in your decision?
Breastfed babies tend to arouse from sleep more easily and sleep for shorter periods of time. Nearly all babies who sleep through the night by 3 months are formula-fed.
Breastfeeding is a major battleground of the modern mommy wars. In her widely discussed piece in The Atlantic, Hanna Rosin called breastfeeding the “new sucking sound”–replacing vacuuming as the task that shackles women to the house, promotes the unequal distribution of childcare and household duties, and prevents women from reaching the upper echelons of professional success. The benefits of breastfeeding have been oversold, she claims, and–just as significantly–the costs to women’s sleep, time, and career progress have been downplayed.
On the other side of the debate, the American Academy of Pediatrics states that the benefits for the infant in terms of reduced risk of infection, adult obesity, allergies, and asthma are so great that breastfeeding must be viewed as an “investment in your child’s future” rather than a “lifestyle choice.” Some lactation consultants fall into this camp too, needing to be reminded to suppress their impulse to sigh when yet another mother complains of exhaustion and lack of sleep, for fear they alienate her–and fail to convince her to keep breastfeeding.
On both sides, well-intentioned but overzealous advocates twist the evidence on breastfeeding, cherry-picking among studies to support their preexisting views.
This is especially true when it comes to one of breastfeeding’s major downsides: disrupted sleep.
Consider the post, 5 Cool Things No One Ever Told You About Nighttime Breastfeeding, which claims that the number 1 coolest thing about nighttime breastfeeding is “breastfeeding moms actually get MORE sleep than their formula-feeding counterparts,” and concludes with the rhetorical question: “Did you ever think, when you hear your baby rouse at 2:00am, that they are actually giving you the gift of MORE sleep…?”
To which I would like to respond: No, never, not only because it does not square with my own experience, but also because the research on this topic is clear: breastfeeding moms, on average, get less sleep, not more.
Almost without exception, studies on formula feeding, breastfeeding, and sleep find that breastfed babies wake up more often than formula fed ones at night, and breastfeeding mothers therefore get LESS uninterrupted nighttime sleep.
Nighttime Wakings in Formula-Fed Versus Breastfed Babies