Every now and then, an article creeps into the news about chemicals contaminating human milk. Who can forget the sensational headlines about rocket fuel in breastmilk (even though a later study also found the substance in infant formula)? Or the ones about a potent neurotoxin in breastmilk? It’s downright scary. In fact, it’s almost enough to make a mother snap up the flaps on her nursing bras forever.

But it shouldn’t be.

An expert perspective
A new study by Judy S. LaKind, PhD sought to measure chemical concentrations in the blood and milk of breastfeeding mothers. The study does find several chemicals in the milk of many of the subjects, but it builds on LaKind’s earlier work, in which she argues that “in studies of breastfed versus formula-fed infants across time, including times when levels of environmental chemicals such as dioxins were higher, beneficial effects of breastfeeding have been found.”

The current study
For the current study, funded by the Research Foundation for Health and Environmental Effects, LaKind and her fellow researchers collected both milk and blood samples from 10 postpartum women, as well as additional milk samples without matching blood samples. Conventional wisdom about organic chemicals in mother’s milk has assumed that initial levels of contaminants are higher because the mother’s lifetime fatty-tissue accumulation of chemicals is exuded into the first milk she produces and that the levels decline over the course of breastfeeding. This study served to explore that assumption.

It didn’t just explore it; it exploded it. The ten women in the study charted unpredictable levels of chemical contaminants at any given time. Each and every chemical showed mixed results; some women had higher levels over time, while others had lower. The variance was highly individualized, too; a particular woman might have an increase in some contaminants and a decrease in others. A given chemical might test higher in a woman’s blood and, at the same time, lower in her milk (or vice versa). While the study population was small, the results nevertheless lead LaKind and colleagues to conclude that the relationship between contaminants and their level in blood/milk is “complex” and possibly “dependent on chemical class.” In any case, they decided that the practice of “pumping and discarding [one’s] early milk as a means of reducing infant exposure” is not helpful.

A couple of caveats about this study: (1) As mentioned above, the study population was very small. (2) The women who participated in the study may or may not have been exclusively breastfeeding; that is, the results may be diluted by some of the mothers feeding their infants formula in addition to breastfeeding. (3) While many studies about environmental contaminants require the participants to have resided in the study area for 10 years (so that the subjects would have greater exposure to the study contaminants), this study only required residency for the previous three years. (4) The study failed to rule out the influence of dietary selections on chemical concentrations, although recent studies (such as this one) suggest that diet may play an important role.

So, is breastfeeding really “best”?
As mentioned above, even Dr. LaKind—who has made measuring levels of chemical contaminants in mothers’ milk a large part of her career—would say yes.

First, she notes in her earlier work, breastfeeding occurs for a relatively short-term period at an early life stage. Second, epidemiological studies do point to a need for change on the governmental level (e.g., regulations for reducing environmental chemicals) but do not show risk of postnatal exposure for individual children. Third, even studies conducted decades ago when the dangerous chemical dioxin was at its highest environmental levels show benefits for breastfed versus formula-fed children—and dioxin levels are much lower now.

Take-home message
Don’t be scared by the hype. Yes, the milk our mothers produce is certainly contaminated with some environmental chemicals. So are the foods we eat (and we can’t think that infant formula isn’t). Given the many benefits of breastfeeding, mothers should still breastfeed.

But that doesn’t mean that we can’t also advocate for better environmental regulations or try to make changes to reduce the chemical load in our bodies. (As a thought-provoking starting point, try The Organic Manifesto of a Biologist Mother, a free download by biologist/author Sandra Steingraber, PhD.)