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Recently, a paper was published on the transfer of perchlorate contaminants in cow and human milk. Perchlorates are common industrial pollutants that are in our water and food supply. While the analytical methods were largely sound in this study, no description was provided on the collection of human samples, so I still have a few problems with this study design. Further, only 36 human breastmilk samples were studied.
Perchlorates are known from earlier studies to impede the iodine pump present in the thyroid gland of mammals. Because this pump is similar to that found in the breast, it is theorized by this study group that high levels of perchlorate may ultimately lead to reduced iodine levels in human milk. This study found some evidence that iodine levels were indeed reduced somewhat, but there was some variability. Because this study had rather limited patients, we’ll have to wait until larger, more definitive studies are available to come to this conclusion.
The most important factor for mothers to understand is that with high perchlorate levels the amount of iodine in their milk MAY be lower, although we're not really sure at this point. But has the incidence of hypothyroidism in breastfed infants increased lately? Not that I know of. I just spoke with one of our Pediatric endocrinologists, and they are not seeing any change in the incidence of hypothyroidism as of yet. It is still averaging about 1 in 4000 infants.
These authors also seemed to suggest that mothers might want to supplement themselves with higher iodine levels. Because iodine is actually pumped into human milk, sometimes at high levels, I worry that the random supplementation of mothers with iodine may actually overdose some infants and cause more problems than we had to begin with. The overdose with iodine is sometimes much worse than the under dose, so I suggest that moms eat iodine-rich foods or iodized salt, but don’t go overboard with iodine or moms really will shut down thyroid production in their infants.
Having spoken with the author of this paper, they in no way wished to imply that mothers should discontinue breastfeeding, only that perchlorates are potentially worrisome and need to be further studied. I would concur with this conclusion.
So, at this time, all mothers should continue to breastfeed and not worry about the perchlorate issue. They should have their pediatricians evaluate their infants at the routine visits for hypothyroidism (which every pediatrician does anyway) and not worry about this contaminate.
In Summary:
1) Perchlorate inhibits the uptake of iodine by the thyroid gland and may work similarly in the human breast.
2) The only known complication from exposure to perchlorates is hypothyroidism, which is easily treated with supplements of iodine or, in rare cases, thyroxine.
3) Be extremely cautious of supplementing with extra iodine, moms may actually do more harm to their infants by overdosing with iodine than by under dosing with "perchlorate".
Lastly, this is the third time in the last several years that environmental contaminates have been found at low levels in breastmilk. This and a lot of other data are suggesting that we humans simply must become more proactive at voting for candidates that support environmental standards because our whole future depends on it. For years environmentalists have called for the reduction of perchlorate in our food and water supplies. It’s time we did something about it !
TomHale Ph.D
Professor of Pediatrics
Texas Tech University School of Medicine
1. Perchlorate and Iodide in Dairy and Breast Milk. Andrea B. Kirk, P. Kalyani Martinelango, Kang Tian, Aniruddha Dutta, Ernest E. Smith, and Purnendu K. Dasgupta. Environ. Sci. Technol.; 2005; ASAP Web Release Date: 22-Feb-2005; (Article) DOI: 10.1021/es048118t |
