Moms, Don’t Feel Ashamed About Your Breast Milk Supply – Even Scientists Are Still Searching For Answers for Why It Isn’t Consistent

Biological underpinnings of breastfeeding challenges
Dr. Kelleher’s Latest Research, found here:

I recently interviewed Dr.Shannon Kelleher, a human milk researcher, about the staggering results from her recent publication “Biological underpinnings of breastfeeding challenges: the role of genetics, diet, and environment on lactation physiology,” published recently in the American Journal of Physiology-Endocrinology and Metabolism. You may remember my two-part interview with Dr. Kelleher about her published research on zinc related to mammary function.

During that series Dr. Kelleher said, “If you think about it, when you’re breastfeeding you have no idea how much milk you are producing or if the composition is optimal and as long as your baby isn’t overtly ill, you assume that everything is working well. But is it?” And that question has echoed in my mind in the years since that post.

Dr. Kelleher’s mission is to use scientific and statistical research to uncover how lactation works, why it can fail, and how diet affects a woman’s ability to produce enough quality milk. After all, the only way it’s possible to best educate and support breastfeeding women in raising thriving well-fed infants is to understand the barriers to feeding them well.

shanShannon L Kelleher, PhD is an Associate Professor in Nutritional Sciences, Surgery and Cell and Molecular Physiology at the Penn State Hershey Cancer Institute. She holds a PhD in Nutritional Biochemistry/Cell Biology from The University of California, Davis, and a B.A. in Biology/Chemistry from the University of San Diego.


Today I’d like to share our recent discussion with you, specifically on those topics – milk production and composition.

Jody Segrave-Daly: The statistics in your introduction are staggering! Can you share them with us, and tell us how many women were studied, how were the numbers derived? And based on what you say, is there any truth to the common teaching that insufficient milk is rare?

Dr. Kelleher: It is shocking isn’t it! The study looks at a sample of participants in the Infant Feeding Practices Study II (IFPS II), which was drawn from 500,000 households in the United States. Approximately 4,900 pregnant women ages 18 and above participated, and of those, 2,000 received questionnaires throughout the first year of their infant’s life between May 2005-2006 (Li et al, Pediatrics 2008).

Here is a snapshot of what we found:

  • Although 75% of new mothers intend to breastfeed, not all women are able to breastfeed their infants exclusively for the first 6 months of life, as recommended by the American Academy of Pediatrics and the World Health Organization;
  • It is estimated that the prevalence of women who overtly fail to produce enough milk may be as high as 10–15%  and can quickly lead to hypernatremia (high blood sodium levels)  nutritional deficiencies, or failure to thrive;
  • The prevalence of lactation “insufficiency” may be much higher, as 40–50% of women in the US and 60–90% of women internationally cite “not producing enough milk” or that their baby was “not satisfied with breast milk” as the primary reasons for weaning prior to 6 months.

Considering these numbers and others like them, I believe the insufficient milk is much more common than we think. If we had a sensitive, reliable, and simple way to assess it then we would be able to really understand how many women are affected by this problem, and most importantly, we could develop solutions to improve lactation performance.

Jody: Exactly. In my lactation practice the overwhelming majority of my moms and babies struggle with mammary function and low weight gain. As their nurse, the only thing I can offer is supplemental interventions and psychological support. What are the known consequences of insufficient milk production to newborn babies? What do high sodium levels, nutritional deficiency, and failure to thrive do to newborns?

Dr. Kelleher: Insufficient milk production can lead to malnutrition and even starvation. When there is not enough milk, babies become dehydrated and that can lead to hypernatremia (high sodium levels) including symptoms such as lethargy, restlessness, hyperreflexia, spasticity, hyperthermia, and seizures. Intracranial hemorrhage (brain bleeds) and acute kidney damage can also become major complications. Nutritional deficiencies in infants, such as insufficient zinc, can lead to chronic skin rashes, poor immune function, failure to thrive (e.g. cognitive and growth delays) and even death.

Jody: Your paper describes the role of genetics, diet, and environment on lactation function. Help us understand your findings so clinicians like myself can use them to help improve breast feeding outcomes. There are many myths that can be found in breastfeeding manuals, like the idea that it is very rare for a mother to not be able to produce enough breast milk.

Dr. Kelleher: There is very little known about genetics and lactation physiology in women. We know a lot more

Copyright: Lee & Kelleher
Copyright: Lee & Kelleher

about the role of genetics on lactation performance in production animals (cows, goats, etc.) because it is driven by the economics of the dairy industry! Of course, one can argue that there are many differences in how lactation works between species, but many of the mechanisms that regulate lactation are likely similar if not identical.

For instance, the general role of prolactin during lactation (the hormone that stimulates breast milk production) is identical. And we currently know that there is huge variability in the volume and composition of milk that women produce. Why couldn’t this be driven by a woman’s genetics?

Jody: What percentage does the role of maternal genetics play into breast milk insufficiency?

Dr. Kelleher: It is estimated that approximately 10-15% of women suffer from overt lactation failure. This is different from what I consider “breast milk insufficiency”. When I talk about “breast milk insufficiency” I’m referring to the inability to make enough milk of optimal quality to feed the baby.

We have already shown that a woman’s genetics is very important to providing enough zinc to breast milk. Others have shown that genetic variation in the vitamin D receptor affects milk calcium levels, and that genetic variation in genes that produce fatty acids, alter the fatty acid composition of human milk. There most certainly will be other genetic factors that are important to milk composition once we start looking!

Currently, we have no idea if/how genetics plays a role in milk volume, but we are very keen to figure this out! In fact, my lab is just starting a research study to look at this question. It’s complicated, given the important roles that appropriate support and education, combined with good nutrition, quality sleep, stress reduction, etc. play in lactation performance.


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