Iodine deficiency ! - falling intakes - goitregens - competition bromine and fluorine

[R.B.]

http://jcem.endojournals.org/content/94/5/1683.long

Title
Thyroid function in early pregnancy in Japanese healthy women: relation to urinary iodine excretion, emesis, and fetal and child development.

Journal
Journal of Clinical Endocrinology & Metabolism 2009 Vol. 94 No. 5 pp. 1683-1688

Abstract

Context: The effect of constant rich iodine intake, especially during pregnancy, has not been well understood. Objective: The objective was to examine urinary iodine excretion and thyroid function in early pregnancy in Japanese healthy women. We also studied fetal maturation and child development in these women. Design and Setting: This study was an observational, prospective study conducted at a maternity hospital. Subjects: Subjects were 622 pregnant women who visited a maternity hospital consecutively in early gestation. Subjects with positive thyroid antibodies were excluded, and finally 514 subjects were examined. Offspring subjects were infants born to the maternal subjects. Main Outcome Measures: Thyroid function, serum thyroperoxidase antibodies, and urinary concentrations of iodine were measured at the initial obstetrical visit. The fetal maturation scores estimated by the Dubowitz and Ballard methods in newly born infants were assessed. A child developmental test was performed using the Enjoji Scale up to 12 months of age. Results: The distribution of urinary iodine concentrations was large, and the average was extremely high. There were significant positive correlations between urinary iodine and serum TSH (r=0.1326; P<0.005). Serum TSH during early pregnancy in mothers had no relevance to parameters in neonates, scores of fetal maturation, or child developmental testing in their infants. Conclusions: Iodine excess during early pregnancy seems to have no adverse effects on the fetus in healthy Japanese women. To avoid hypothyroidism, reducing excess dietary iodine intake to moderate intake may be beneficial for pregnant woman in Japan.


The official Japanese recommendation appears to be 3mg; the chart of urinary iodine shows intakes ranged widely and some were very high.

"Considering all the various factors together, the limit of iodine intake for healthy Japanese pregnant women should be around 3000 μg iodine/d, as recommended by the Japanese Health, Labor and Welfare Ministry (9)."

[R.B.]

The above paper begs the question how well does iodine intake and urinary iodine correlate. This paper goes some way to confirming in general terms a strong correlation.

http://www.ymj.kr/Synapse/Data/PDFDa...ymj-39-355.pdf

Clearly the difficulties in assessing iodine intake because of the large variations due to processing and food preparation are significant.

But based on this paper it can be reasonably assumed that high urinary outputs do correlate with high intakes, so based on urinary iodine output cited in the papers above we can be certain that some Japanese do indeed consume significant amounts of iodine; further generally there is no indication that this intake has negative health consequences.

Of course nothing is ever simple, so higher urinary outputs for a given intake in some could be due to other factors including differences in transporter function, historic intake and so levels of tissue saturation including fat and muscle, absence of intake of iodine uptake blockers in so far as they can affect net uptake through the gut iodine transporters, other dietary differences such as polyunsaturated fat intake etc. It appears much is still unknown.

However overall if you have not at some point ingested the iodine it is not possible to excrete it, so it is inescapable that on a population basis higher excretion must point to higher intake.

I would find it surprising if nobody has looked at uptake and excretion in population groups known to have a high long term intake of iodine, but have not come across any such papers so far.

In the table in this paper the UK and USA have the lowest intakes, indeed the UK ranks towards the bottom of a global ranking of iodine intakes; no 7 in a list of "The top 10 iodine-deficient countries (based on national median UIC <100 μg/L) with the greatest numbers of SAC with insufficient iodine intake in 2011. SAC, school-age children; UIC, urinary iodine concentration." Fig 3 http://nutrition.highwire.org/content/142/4/744.full

[R.B.]

I have removed this post as the link seems temperamental which is a shame; and the post has no point without the link.

More in the next day or so - the antibacterial effects of iodine are currently on my mind.

Apologies for any inconvenience