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An increase in salt iodination improves iodine nutrition in children and pregnant women
The background of the study. Iodine is an essential
nutrient, and iodine supplementation is required to prevent iodine
deficiency in most countries. Iodine intake can decline as a result
of a decrease in intake, which can be caused by a decrease in salt
intake (the food usually supplemented with iodine), changes in food
processing, and changes in animal care practices. During the 1990s
iodine intake declined in Switzerland, which led to an increase
in the iodine content of salt. This study was done to determine
the effect of the increase in salt iodination in that country.
How the study was done. Iodine was measured in urine samples collected from children in primary school and from pregnant women throughout Switzerland between April and December 1999 and April and September 2004. The iodine content of salt had been increased from 15 to 20 mg/kg in 1998. In addition, the results of blood-spot thyrotropin (TSH) measurements in newborn infants for 1992–1998 and 1999–2004 were obtained from the records of the screening program for hypothyroidism.
The results of the study. In the children, the urinary iodine concentration increased from 115 µg/L in 1999 to 141 µg/L in 2004, and the proportion of children with values >100 µg/L (indicating iodine sufficiency) increased from 60 to 76 percent. In the pregnant women, the urinary iodine concentration increased from 138 µg/L in 1999 to 249 µg/L in 2004, and the proportion with values >140 µg/L (which corresponds to an intake of 200 to 220 µg/day, the recommended intake for pregnant women) increased from 48 percent in 1999 to 77 percent in 2004.
Blood-spot TSH concentrations were >5 mU/L in 2.9 percent of 259,035 newborn infants from 1992 to 1998 and 1.7 percent of 218,665 newborn infants from 1999 to 2004 (P<0.01), a change also indicative of increased maternal iodine intake.
The conclusions of the study. Increasing the iodine content of salt by 25 percent substantially increases urinary iodine excretion in children and pregnant women.
The original article. Zimmermann MB, Aeberli I, Torresani T, Burgi H. Increasing the iodine concentration in the Swiss iodized salt program markedly improved iodine status in pregnant women and children: a 5-y prospective national study. Am J Clin Nutr 2005;82:388-92.
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| Thyroid Digest Index | | | November 2005 Thyroid Digest |
