Breast Milk Is The Best Milk

Kudos for the article “Deconstructing Breast Milk” (C&EN, July 8, page 28). In 2005, my colleagues and I reported the near-universal finding of perchlorate in the milk of U.S. mothers (Environ. Sci. Technol., DOI: 10.1021/es048118t).

Perchlorate is of concern because human NIS, the sodium iodide protein that transports iodide from the bloodstream to the thyroid gland, takes up perchlorate with much greater affinity than iodide. In effect, perchlorate is an iodide transport inhibitor and can potentially cause iodine deficiency. This is of concern in a population where, contrary to popular belief, a significant segment of the U.S. population is barely iodine sufficient.

Pregnant and expectant mothers are of particular concern because the thyroid hormones control neurodevelopment. A 2004 study of 100 expectant mothers in Boston found 49 to have inadequate iodine intake, 15 of them acutely so (Thyroid, DOI: 10.1089/105072504323031013). Unfortunately, our study, much publicized in the popular press, led some breast-feeding mothers to believe that we were suggesting that mothers not breast-feed. After getting several e-mails accusing me of being in the coattails of formula manufacturers, I was forced to write an open letter to a prominent website catering to breast-feeding mothers stressing that this is not the case (http://kellymom.com/bf/can-i-breastfeed/chemicals/dasgupta-response). We wanted to tell breast-feeding mothers that they should pay special attention to their iodine nutrition.

Full absolution came in 2012 when we reported that breast-fed infants can actually metabolize a good fraction of ingested perchlorate, whereas formula-fed infants apparently cannot (Environ. Sci. Technol., DOI: 10.1021/es2042806). The difference was attributed to the very different bacterial population in the gut.

Purnendu K. Dasgupta
Arlington, Texas