Iodine is an essential mineral for the synthesis of thyroid hormones required for normal growth – so obviously critical for the development of newborns. Deficiency during this period can cause growth delay, impaired hearing and reduced cognitive function.
Globally, 1.9 billion people have iodine deficiency, and is the most preventable cause of intellectual disability. Therefore, pregnant and lactating women are encouraged to increase their intake to compensate for loss through breastfeeding.
WHO (World Health Organization) recommends a daily intake of 250 μg/d for lactating women. This helps ensure both mother and child get enough, while the Universal Salt Iodization (USI) programme has also sought to control such deficiency in the general population.
However, according to researchers from China, few have delved into the possible adverse effects of over consumption of this trace element. Building on Korean research a few years back, the scientists looked at 343 healthy lactating women living in areas of China with either low, adequate or excessive iodine water content.
They found the prevalence of thyroid disease in lactating women, particularly subclinical hypothyroidism (or an 'underactive thyroid gland'), was significantly higher in those with excess iodine intakes compared to those living in the ‘sufficient’ areas.
“Excessive iodine intake may induce subclinical hypothyroidism in lactating women. Moreover, adequate iodine nutrition is essential for lactating women and infants, especially those living in iodine-deficient areas.
“Enhanced monitoring of iodine status is important to avoid adverse effects of iodine deficiency or excess, particularly in susceptible populations such as pregnant or lactating women and infants,” the researchers concluded.
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Source: The relationship between iodine nutrition and thyroid disease in lactating women with different iodine intakes