Low breastmilk supply may be genetic


One of the most pernicious of the many pernicious aspects of breastfeeding promotion is the insistence by lactation consultants that all women can make enough breastmilk to fully nourish an infant.

Not only is it factually false, but it has given impetus to two additional erroneous beliefs:

1. Insistence that low supply is a misperception on the part of the mother

2. Belief that documented low breastmilk supply, and the relentless infant hunger that results, is the mother’s fault.

The assumption (sometimes stated, often implied) is that women who have low supply aren’t trying hard enough, aren’t breastfeeding often enough and long enough, aren’t pumping enough, shouldn’t have had an epidural or C-section, never should have let the baby have a pacifier, etc.

[pullquote align=”right” cite=”” link=”” color=”” class=”” size=””]Low breastmilk supply is as real as diabetes. [/pullquote]

These are incredibly harmful beliefs. First, they hurt new mothers who are desperately trying to breastfeed without success. The only thing more devastating than hearing your baby scream incessantly from hunger is being told that it is only your imagination or worse, the result of your selfishness. It’s the equivalent to insisting that those with type I diabetes lack insulin because they are too lazy to produce it.

Fortunately, within the past year or so, increasing attention has been paid to the harmful impact of such claims on maternal mental health. Women have been sharing their stories of guilt, shame and depression and pushing back against the overwhelming pressure to breastfeed exclusively.

The second harmful aspect of such beliefs often goes overlooked. By insisting that low breastmilk supply is imaginary or simply a matter of maternal effort, lactivists have systematically failed to investigate biological causes of low supply. That’s the equivalent to refusing to look for a cause of type I diabetes and blaming diabetics instead.

The truth is that low breastmilk supply (like diabetes) is real, is no one’s “fault” and has a biomarker to prove it.

Earlier this year I wrote about the discovery of a biomarker for low breastmilk supply: high sodium concentration within breastmilk.

High levels of sodium in breast milk are closely associated with lactation failure. One study showed that those who failed lactation had higher initial breast milk sodium concentrations, and the longer they stayed elevated, the lower the success rate. This association has subsequently been confirmed.Several possibilities have been suggested as to the cause of increased sodium levels in breast milk… It has been shown that sodium values are not affected by the mother’s diet or by the method of milk expression …

Subsequent research demonstrated that women who expressed concerns about breastmilk supply were more likely to have the biomarker than women who did not.

If concerns about milk supply among exclusively breastfeeding women were primarily owing to a lack of knowledge about the signs of abundant milk production, then the expected outcome would be no difference in breast milk Na:K as compared with exclusively breastfeeding women without milk supply concerns… Instead, the observed prevalence of elevated Na:K was 2-fold greater in the mothers with milk supply concerns (42% vs 21%)… This result challenges the belief that milk supply concern in the context of exclusive breastfeeding is primarily maternal misperception.

These findings also challenge the belief that all women make enough breastmilk to fully nourish an infant and it is their fault if they don’t.

Now comes evidence of a genetic basis for low milk supply. Milk cell gene expression of mothers with low breast milk production is a basic science paper with important clinical implications. It was funded by a grant from Medela AG, a maker of breast pumps.

Initial analysis found cells isolated from women with low milk production showed significantly lower expression of the genes estrogen related receptor beta (ESRRB, p=0.027) and neurotrophin receptors sortilin (SORT, p=0.010) and tyrosine receptor kinase 2 splice variant 1 (TRKB1, p=0.007) and higher expression of a progenitor marker (REX1, p=0.025) compared with cells isolated from women with normal production.

The authors concluded:

Preliminary findings suggest variations in cell signalling and function, examined through gene expression that might contribute to low milk production. Further investigations will potentially determine significant roles of key genes enabling successful human lactation.

This shouldn’t be surprising. Genes control everything from height to eye color to susceptibility to disease. Why wouldn’t they also control breastmilk supply?

By investigating the biological basis for low milk supply we can find the cause and, hopefully, a cure. Alternatively, we may find that as with type I diabetes, no cure is currently possible, and supplementing (with insulin in diabetes, with formula in low breastmilk supply) is the only course of action. In either case, it should relieve the stigma on new mothers with low supply.

Low breastmilk supply is as real as diabetes and it poses a substantial health threat to infants. It’s not a mistaken maternal perception; it’s not mothers’ fault; and it can’t be fixed with greater maternal effort.

It’s almost certainly genetic.