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Letters to the Editor |
Forschungsinstitut für Kinderernährung (Research Institute of Child Nutrition), Heinstück 11, 44225 Dortmund, Germany
The most widely used biochemical indicator for the assessment of iodine status is urinary iodine excretion (1, 2). Endemic goiter and low urinary iodine excretion levels have been scientifically documented for decades and are still present in Europe (3, 4). In Germany (and similarly in a number of other European countries) the major cause of this is the legislation on micronutrient fortification, which still does not allow or lay down the mandatory iodization of foods.
After it became clear that increasing the iodine content of iodized table salt from 5 to 20 mg/kg, enforced in 1981, only marginally improved the iodine status of the German population, additional legislative measures were undertaken. In 1989 it became legal to add iodized salt to industrially processed foods and to canteen meals; then in late 1991 the use of iodized salt in the pickling of meat and sausages was legalized, and finally a decree issued in December 1993 superseded the previous law where the use of iodized salt in the food processing had to be separately labelled and declared by all food producers.
To evaluate the effects of the above stages in the German "iodine
deficiency prophylaxis programme" urinary iodine excretion rates were
measured along with body weight and body height in 541 healthy children
aged 3–18 yr from 1986–1997. All the children studied were
participants in the DONALD (Dortmund Nutritional and Anthropometrical
Longitudinally Designed) study, a prospective mixed longitudinal cohort
study on nutrition, growth, and metabolism from birth to maturity.
Urinary 24-h iodine excretion rates were related to individual body
surface area (standardized to adult body surface area of 1.73
m2) to fully control for the age dependency of urinary
iodine output during growth (5). External iodine contaminations of the
24-h urine samples were avoided (6). Each child collected one 24-h
urine sample per year and contributed between 1 and 12 specimens to the
total number of 2404 urine samples analyzed during the 12 year
observation period. As shown in Fig. 1
, the very low urinary iodine excretion level seen in 1986 was still
present in 1992 (median output: 66 and 71 µg/day/1.73 m2,
respectively corresponding to a median urinary iodine concentration of
68 and 67 µg/L, respectively). Thereafter, a steady increase
occurred, and a median output of 99 µg iodine/day/1.73 m2
was reached in 1997 (corresponding to a still insufficient (4) median
urinary iodine concentration of 95 µg/L). Cross-sectional statistical
analysis (ANOVA) on the logarithmic transformed data followed by
t-tests revealed a significant (P < 0.05)
rise in urinary iodine excretion (µg/day/1.73m2) one year
after the third legislative measure (i.e. from 1993 to 1994)
but no significant (P > 0.1) increase one year after
the first (from 1989 to 1990) or the second (from 1991 to 1992)
measure.
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We acknowledge support by grants from the Forum Schilddrüse e. V.
Footnotes
Address correspondence to: Thomas Remer, Research Institute of Child Nutrition, Heinstück 11, Dortmund, Germany 44225.
Received July 24, 1998.
References
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