reported to have mean concentrations of iodine in milk of 454 mg/
L.20 In Australia, the iodine concentration in milk fell from 593 mg/L
in 1975 to 195 mg/L in 2004.21 The authors of this study suggest that,
as no active iodine prophylaxis policy exists in Australia (with
iodized salt), the reduced amount of iodine in milk is likely to be
one of the explanations for the re-emergence of iodine deficiency in
Sydney and perhaps elsewhere in Australia. In the Czech Republic,
the iodine concentration in cow’s milk rose from a mean of less
than 50 mg/L in 1982 to over 300 mg/L in 2005, with 16% of samples
above 500 mg/L.22 In Peru, the iodine concentration in cattle milk
varies from 24 mg/L in the region of Cajamarca to 170 mg/L in Lima.23
Iodine deficiencywas well-known in Great Britain, at least up to the
1950s. Although Great Britain has never had mandatory iodization
of salt and other foods, iodine intake has increased, especially since
the 1970s and up to the early 1990s. Increased iodine intake is
mainly due to changes in farming practice that have resulted in
more iodine in milk and other dairy products.24