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| FOR IMMEDIATE RELEASE Sept. 17, 2003, 2:45 p.m. EDT |
For more information, please contact the ATA at thyroid@thyroid.org. |
Breastfeeding Mothers Who Smoke May Reduce Iodine Available
to Their Infants
(PALM BEACH, FLA., Sept. 17, 2003) - If a nursing mother
smokes, breastfeeding may endanger brain development in the infant due
to iodine deficiency, according to first-time findings of a study being
presented today at the 75th Annual Meeting of the American Thyroid Association.
"Breast-feeding mothers should not smoke," advised Peter Laurberg,
MD, lead author of the study and professor of endocrinology at Aalborg
Hospital in Aalborg, Denmark, "but if they do, it is important that
they obtain sufficient iodine from their diet or from iodine-containing
supplements."
Sufficient iodine intake is necessary for normal brain development during
the first years of life. During breastfeeding, thyroid function of the
infant depends on iodine in breast milk. The World Health Organization
reports that each year many millions of children are born without proper
iodine nutrition to safely protect brain development.
Dr. Laurberg and colleagues hypothesized that smoking may be a culprit
because of the link between thiocyanate, a by-product of tobacco that
accumulates in blood and tissues of smokers, and the reduced ability for
the body to transport iodine to the thyroid gland. Specifically, it is
thought that thiocyanate affects the proper functioning of a biological
pump, called the natrium-iodine symporter (NIS), which is present in the
lactating mammary gland. NIS is also responsible for iodine transport
in the thyroid gland.
The researchers studied 140 pregnant women admitted for delivery after
an uncomplicated pregnancy and their newborn infants. Fifty women were
classified as smokers based on urine and blood tests. The researchers
found that smoking and nonsmoking mothers had identical urinary iodine,
but iodine content in breast milk was reduced by almost 50 percent in
smoking mothers. They also observed that the urinary iodine excretion
of breastfed children is low, a signal of iodine deficiency. In addition,
the findings suggest that these children have an impaired ability to use
even the small amounts of iodine provided in milk when the mother is a
smoker.
"The more smoking, the more reduction in iodine content," added
Dr. Laurberg. "The reduction in milk iodine content correlates to
the blood concentration of thiocyanate in the mothers."
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