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Posts tagged ‘Breastfeeding’

Why Care About Breastfeeding Research?

Since becoming a mom, and especially since starting this blog, I have paid particular attention to new breastfeeding research. After all, my training is in nutrition, and breast milk is one of the most interesting foods around. Plus, I’m currently lactating and still breastfeeding my daughter a few times per day, so it’s on my mind.

When I look back at the papers that I have covered and those that I find on other blogs and media outlets, I notice that many focus on how breastfeeding improves outcomes in babies.

But I also notice that when I blog about breastfeeding research, I have to spend a big chunk of the piece talking about the limitations of the study. Breastfeeding research – at least when conducted in humans – will always have big limitations that require disclaiming and explaining. The problem is that it is impossible to randomize breastfeeding trials or to “blind” the subjects to feeding type. It is difficult to know, despite the fanciest statistical methods, if it is breast milk that makes those babies thinner, smarter, stronger, cry more, etc, or if there are other factors at play in this complex thing called human life. Sometimes, by the time I’ve listed the problems with interpreting a breastfeeding study, I wonder if these findings were actually meaningful, and I’m sure my readers feel the same way.

Elsewhere around the Internet (not so much on my blog), I often see comments to this effect on articles about the latest research on the benefits of breastfeeding:

“Another useless study. Obviously we mammals were meant to feed our babies breast milk. I don’t know why scientists waste their time and our money with this stuff.”

Why bother doing more research on outcomes associated with breastfeeding? It is pretty clear that breastfeeding is a great way to feed an infant. Maybe it is time to stop oohing and awing over breast milk. Read more

Bottle-feeding and Obesity Risk

Source: Wikimedia Commons

A study published this month in Archives of Pediatric and Adolescent Medicine looks at the relationship between infant feeding practices and weight gain (1). Breast milk vs. formula? Nope, it isn’t that simple.

Led by Dr. Ruowei Li of the CDC, this prospective longitudinal study tracked feeding and weight gain in 1900 infants during their first year of life. Each month, mothers were asked how they fed their babies in the last 7 days, and from their replies, infants were grouped into the following categories across ages:

  1. Breastfed only
  2. Breastfed and human milk by bottle
  3. Breastfed and formula by bottle
  4. Human milk by bottle only (i.e. exclusive pumping)
  5. Human milk and formula by bottle
  6. Formula by bottle only

The mothers in this study were mainly white, married, and had at least a high school education. A third were on WIC. About 50% were overweight or obese. Statistical methods were used to adjust the findings for a range of maternal factors, including BMI, as well as infant sex, gestational age, birth weight, and age of solid food introduction.

The most important finding from this study was that infants fed by bottle only – whether fed formula or breast milk – gained more weight than those fed breast milk at the breast. Read more

Breastfeed for your child’s future… as a long-jumper?

I try to stay abreast of the latest in breastfeeding research (hehe), and this paper, published last week, caught my eye:

Exclusive breastfeeding duration and cardiorespiratory fitness in children and adolescents. (Labayen et al., American Journal of Clinical Nutrition)

Was it possible that breastfeeding BabyC could affect her level of fitness as a teenager? I was intrigued.

The study tested cardiovascular fitness on a stationary bike in about 2000 children and teenagers from Sweden and Estonia. The kids’ mothers were asked to recall if they breastfed their children, and if so, for how long (<3 months, 3-6 months, or >6 months). Children that were fed a mix of breast milk and formula for any period were eliminated from the study.

The researchers found that breastfed kids had about 5% greater cardiovascular fitness than those fed formula, and fitness was highest in children who had been breastfed exclusively for at least 3 months. This finding held true even after the researchers adjusted for country, gender, age, puberty, BMI, birth weight, physical activity level, maternal BMI and maternal education.

A 5% increase in cardio fitness may not seem like much, but it is actually rather impressive when you consider all the other factors that are involved. Genetics are thought to explain about 50% of fitness, and body weight and activity level (how much aerobic activity a person routinely does) also play a big role.

As often happens when I read journal articles, this study led me to another published in 2010. Among more than 2500 teenagers from around Europe, Enrique Artero and colleagues found a significant correlation between how long they were breastfed as infants and how far they could long jump. Boys that were breastfed for 6 months or longer had an 11-cm edge over formula-fed boys, and girls had a 7-cm edge. On the other hand, there was no association between breastfeeding and speed in the 20-meter shuttle run. (That sure brings back memories from middle school!) Like the previous study, these data were adjusted for factors like the children’s physical activity and body composition and parental weight and education.

So breastfeeding my child means she’ll be better at both cycling and the long jump?!

Not so fast. You know I’m not going to report the results of new research without talking about its limitations. Both of these studies are retrospective, cross-sectional studies. They looked at kids that were breastfed and those that weren’t and compared their physical fitness. In an ideal world, if you wanted to know if breastfeeding was related to physical fitness later in life, you would enroll a bunch of pregnant women and assign them to either the breastfeeding group or the formula-feeding group. Then, 10-15 years later, you would run their kids through physical fitness tests. We all know that this type of prospective, randomized trial will never happen. No mother is going to let a researcher tell her how to feed her baby. Instead, each mother makes that choice herself, and there are many factors that contribute to her choice.

These types of retrospective, cross-sectional studies of breastfeeding always have one big flaw: they simply can’t account for every factor that may be different between breastfeeding and formula-feeding mothers. My guess is that the researchers have only scratched the surface by including maternal BMI and education in their statistical models. What about exercise during pregnancy? Or mom’s nutrition during pregnancy and lactation? How about exposure to cigarette smoke? These are all factors that might be different between breastfeeding and formula-feeding moms. Any of these factors, in addition to breastfeeding, might influence children’s later fitness level by epigenetic mechanisms or more directly, such as by affecting the rate and timing of muscle growth. Research on the benefits of breastfeeding is very hard to do.

As a skeptic and a scientist, I tend to think that this fitness effect is not just about breast milk but probably intertwined with other factors. But as a nursing mom, it is kind of cool to think about. I’ve tried to tell my daughter that the long jump may be in her future, given her 7 cm edge. She doesn’t seem to care. She has been practicing athletic feats during our recent nursing sessions, but they are more yogic in nature. I swear she did a one-legged downward dog the other day without breaking her latch!


Artero EG, Ortega FB, Espana-Romero V, Labayen I, Huybrechts I, Papadaki A, Rodriguez G, Mauro B, Widhalm K, Kersting M, et al. 2010 Longer breastfeeding is associated with increased lower body explosive strength during adolescence. J Nutr 140 1989-1995.

Labayen I, Ruiz JR, Ortega FB, Loit HM, Harro J, Villa I, Veidebaum T & Sjostrom M 2012 Exclusive breastfeeding duration and cardiorespiratory fitness in children and adolescents. Am J Clin Nutr. Published online ahead of print 01/11/12.

Can Breast Milk Cure My Child’s Eye Infection?

Breast milk provides optimal nutrition for infants, and it gives them immune protection that no formula company has been able to replicate. How many other secrets does it contain? Many mothers claim that it is also an effective treatment for eye infections, or conjunctivitis. The anecdotal evidence for this practice is overwhelming, but is there any scientific evidence that it actually works? Read more

Breastfeeding Beyond a Year: Why Stop Now?

BabyC is fast approaching her first birthday, and I’ve been asked more than a few times, “How long do you plan to keep breastfeeding?”

When I first started thinking about this question, the scientist in me wondered about the health benefits of “extended” breastfeeding.  I wrote about some of my research on the (purported) health benefits of nursing beyond a year last week.  I plowed through hundreds of breastfeeding studies looking for some data on extended breastfeeding, but the truth is that very little research on this topic has been published, and almost nothing has been published on extended breastfeeding in the developed world.  Please let me know if I missed something – just don’t send me links to La Leche League and KellyMom.  I’ve seen their pages and tracked down all those citations, and I couldn’t find any convincing evidence that my child will be any less healthy or nourished or smart if I wean at a year.  There could very well be health benefits to extended nursing, but as far as I can tell, they haven’t been described in the scientific literature.  I doubt if that will change in the near future, since extended breastfeeding is probably not much of a research priority.

However, as I started delving into the research on this topic, I realized that the mother in me didn’t really care what the data saidRead more

Breastfeeding Beyond a Year: Why Is the AAFP Stretching the Truth About the Benefits?

The benefits of breastfeeding to a young infant’s health are well-documented (though sometimes debated), and the American Academy of Pediatrics (AAP) recommends that babies be breastfed for the first year of life if possible.  Are there any health benefits to the child for breastfeeding beyond a year?  I am curious about this as my daughter approaches her first birthday.

Photo credit: Santiago Fernánde. via Wikimedia Commons

I shouldn’t have been surprised to find that there have been very few studies of extended breastfeeding (> 1 year) conducted in the developed world.  Breastfeeding research is notoriously hard to do, and good research on extended breastfeeding is nearly impossible.  As a population, women in the developed world who breastfeed their babies are already likely to be different from mothers who choose not to breastfeed, setting their babies up for different outcomes well before their boobs even hit the baby’s lips.  (This is of course a very broad generalization, and I recognize there are exceptions.)  These differences are likely even greater in women who choose to breastfeed beyond a year.  Only 24% breastfeed to one year in the U.S. [1], and we don’t know how many continue beyond that.  These mothers are more likely to be well-educated, white, older, richer, buying organic food, fretting about BPA exposure, and the list goes on.  Sure, we can use statistics to try to account for these confounding variables, but these methods require (A) that you’ve identified the most important variables, and (B) that you have study participants that represent a spectrum along that variable.  This research is hard to do. Read more

Why Is Breast Milk So Low in Iron?

When I started feeling concerned about BabyC’s iron status (Does My Baby Get Enough Iron?), I did what most worried, sleep-deprived mamas do – a Google search.  What I found were pages and pages of forums and blog posts full of comments from breastfeeding mothers who couldn’t fathom that their baby wasn’t getting everything she needed from breast milk.  Feed an iron-fortified cereal or give my baby iron drops?  Why?  Isn’t breast milk the perfect food for my baby?  I found many mothers fiercely defending breast milk and accordingly delaying the introduction of complementary foods and shunning the use of any fortified foods or supplements.  I felt compelled to write about this, because I think that in some circles the enthusiasm for breastfeeding has swung a little too far outside of what is actually best and natural for babies. Read more

Interpreting infant growth charts

Remember your first visit with your baby’s pediatrician?

I remember that it seemed like a HUGE deal just to leave the house.  Did we fasten BabyC in the car seat correctly?  Where can we sit in this waiting room where there will be 0% chance of a sick kid coughing on her?  OMG, she’s crying!  How long will we have to wait?  Should I feed her?  Yes, let’s try that.  (First time nursing in public.)  Five minutes later, when I had finally situated the baby and arranged the nursing cover and gotten a proper latch, the nurse called us back to the examining room… That’s what I remember.

Oh, but our visit with the pediatrician – what do I remember about that?  Two things.  First, he told me that, even though it seemed like my baby was nursing for 45 minutes out of every hour of the day, my milk may not come in for another 2 or 3 or 4 days.  And my baby might get a little hungry.  Great.  Second, the nurse weighed our baby and measured her length and head circumference.  Then we got those all-important percentile stats that told us how our baby compared to her peers.  So began a lifetime of pretending not to care how our baby measured up. Read more

New Study: Exclusive Breastfeeding Can Support Infant Growth to 6 Months of Age

A new study published this week in the journal Pediatrics found that exclusive breastfeeding up to six months provides enough calories for infants.

Quick and Dirty Summary:

This study addressed two common concerns about breastfeeding:  1) Many moms simply can’t produce enough milk for their babies; and 2) Exclusive breastfeeding, while adequate in younger infants, may not provide enough calories for babies up to 6 months of age.  The data from this study indicate that when moms are given breastfeeding support, milk production is not a limiting factor and provides enough calories for normal growth, even in 6-month-old infants.  However, this study was small and had several limitations (which I will discuss).

Read more

5 Practical Ways to Increase Iron in Your Baby’s Diet

I mentioned in my last post (Does My Baby Get Enough Iron?) that I have been worrying about my 9-month-old’s iron nutrition.  Iron deficiency can cause lasting delays and deficits in cognitive and behavioral development, and I don’t want to go there.

First, let’s consider if your baby is actually at risk for iron deficiency, because why fret about something that isn’t a problem?  You have enough to worry about.

Read more