A survey by Brazil’s University of São Paulo School of Medicine (Faculdade de Medicina da Universidade de São Paulo) (FMUSP) has found that an excess of iodine in table salt between 1998 and 2003 has probably caused a spike on thyroid gland diseases.
FMUSP took urine samples from 2,089 children between the ages of 7 and 14 between 2001 and 2002 and found that 70% of them had excess iodine.
Normally a person has 100 to 119 mcg/l (micrograms of iodine per liter of urine); some of the children in the survey had up to 300 mcg/l.
According to Dr. Geraldo Medeiros Neto at USP, "We are led to believe that the excess of iodine causes a greater frequency of chronic thyroid inflammation. But this is a time bomb in that the effects will only occur later, mainly in people with a genetic disposition for thyroid diseases."
In 1998, the Health Vigilance Secretariat (Anvisa) ordered an increase in the amount of iodine in table salt due to a surge in cases of goiter in Brazil.
The new Anvisa rule permitted a ceiling of 100 milligrams of iodine per kilo of salt. In 2003, the ceiling was reduced to what it had been before 1998: 60 mg.