This paper is full of thought provoking material including these two references to the use of iodine for water purification in prison populations.
It makes the point in the introduction that cooking losses of iodine can be significant, which is both of relevance to us in the west and in assessing Japanese iodine intakes.
"The iodine content of raw food is reduced by cooking (WHO, 1996). For example, the iodine loss on boiling or grilling/frying fish was 50-82 and 20% respectively (Harrison et al., 1965)."
It also suggest that absorption of iodine in food may only be 50%.
"22. Inorganic iodine is readily absorbed from the gut, generally as iodide (Nordic Project Group, 1995). However, probably only 50% of iodine present in organic compounds in foods is absorbed (Bender and Bender 1997). Though some absorption occurs in the stomach, the small intestine appears to be the principal site of absorption in both humans and rats (Riggs, 1952, Small et al., 1961)."
I have been looking for but unable to find any papers looking at the effect of thiocyantes / perchlorate / nitrates etc on the iodine importers in the gut (if any)
Logically losses in the gut and in food preparation need to be considered in making any dietary recommendations.
Vegans are reported to be at particular risk of low iodine levels.
"40. It has been reported that vegans and vegetarians can consume inadequate intakes of dietary iodine. A controlled experimental diet (performed in Germany, a classical iodine deficient country until the mid 1990s) used a repeated measure method (Remer et al., 1999). It exposed six adult volunteers to a 5 day dietary intervention in which isoenergetic lactovegetarian and non vegetarian diets were
consumed. The strict vegetarian diet produced both an extremely low iodine intake (<20 μg/d) and urinary output (36.6 (SD 8.8) μg/d). The authors concluded that strict vegetarians are possibly at risk of developing iodine defciency disorders."
The risks associated with low intake could possibly be added to increased thiocyanate intake in basicas by virtue of higher vegetable intake, and increased goitrogens in soy by virtue of a higher intake of soy products
Could the high levels of hypothyroidism in Whickham (UK) Par 65 be maybe due to high fluoride intake from sources unknown - industry or water etc
EXPERT GROUP ON VITAMINS AND MINERALS
http://www.google.co.uk/url?sa=t&rct...56146854,d.d2k
EVM/00/06.REVISEDAUG2002
__________________________________________________ _______________________________33
This paper has been prepared for consideration by the Expert Group on Vitamins and Minerals and
does not necessarily represent the final views of the Group.
136.The health and thyroid function of representative subjects of a prison population
(initially 133 euthyroid prisoners though due to discharge this number was
gradually reduced to 70) was assessed before and during usage of iodinated water
for 9 months (Freund et al., 1966). Water containing 1 mg/l iodine induced a
marked decrease in the uptake of radioactive iodine to 7% but protein bound
iodine levels did not change significantly until the iodine concentration was
increased to 5 mg/l for 2 months (following 7 months exposure at the lower
level), resulting in a decrease of radioactive iodine to 2%. Serum thyroxine
concentration did not change regardless of the iodine concentration. No
information on actual intake is provided but it can be assumed that water
consumption would be approximately 2 litres/day. The authors noted that
prisoners continued to receive iodine from the diet including the use of iodised
salt. It was also noted that no effects on thyroid function were found in nonprison
personnel who swam in water iodinated at a level of 5 mg/l. No evidence
of iodine allergy was apparent. Two of fifteen male inmates who had had
consumed water containing 1 mg I/l for at least 3 months, had impaired iodine
organification (as measured by the change in thyroidal 131I concentration
following administration of perchlorate). The clinical significance of this effect is
unclear as individual T4 concentrations remained unchanged throughout the
study i.e. no patients demonstrated iodine-induced hypothyroidism.
137. As a continuation of the study discussed above, iodination of a prison water
supply at a concentration of 0.5 to 0.75 mg/l (estimated intake 1-1.5 mg/day) for
up to15 years did not result in any change to serum thyroxine level (Thomas, et
a., 1978). During the same period, 177 women in the prison gave birth to 181
full term infants without any enlargement of the thyroid being noted in the infants
(Stockton and Thomas, 1978). The mothers of 101 infants had been in prison for
≥122 days, whilst 80 mothers had been incarcerated for < 118 days (10-118).
However, the symptoms of 4 women who were hyperthyroid before entering,
worsened.