children birth–6 months: RDA 110 mcg; UL not
available
children 7–12 months: RDA 130 mcg; UL not
available
children 1–3 years: RDA 90 mcg; UL 200 mcg
children 4–8 years: RDA 90 mcg: UL 300 mcg
children 9–13 years: RDA 120 mcg; UL 600 mcg
adolescents 14-18 years: RDA 150 mcg; UL 900 mcg
adults 19 years and older: RDA 150 mcg; UL 1,100
mcg
pregnant women under age 19: RDA 220 mcg; UL
900 mcg
pregnant women age 19 and older: RDA 220 mcg;
UL 1,100 mcg
breastfeeding women under age 19: RDA 290 mcg;
UL 900 mcg
breastfeeding women age 19 and older: RDA 290
mcg; UL 1,100 mcg
Sources of iodine
Iodine must be acquired from diet. Marine plants
and animals, such as cod, haddock, and kelp (sea-
weed), are an especially good source of iodine because
they are able to concentrate the iodine found in sea-
water. Freshwater fish are a less good source. Plants
contain varying amounts of iodine depending on the
soil in which they are grown.
In industrialized countries, feed for cattle, chick-
ens, and other domestic animals is often fortified with
iodine. Some of this iodine finds its way into animal
products that humans eat— milk, eggs, and meat. In
developing countries where feed is not enriched or
cattle are raised on grass, these animal products do
serve as a source of iodine.
Commercially processed foods are often made
with iodized salt. The iodine content of salt changes
very little during processing. Sometimes an iodine-
containing stabilizer is added to commercial bread
dough. This increases the iodine content of bread.
The stabilizer is used less often now than it was in the
twentieth century. However, for many people, com-
mercially processed foods are their main source of
iodine. Iodine is also found in most multivitamin
tablets.
Iodine can be absorbed through the skin from
iodine-based disinfectant solutions. Automobile exhaust
puts some iodine into the air, and this can be absorbed
through the lungs. Neither of these provide significant
amounts of iodine for most people.
The following list gives the approximate iodine
content for some common foods:
kelp, 1/4 cup wet: 415 mcg or more. Amount is highly
variable
salt, iodized, 1 g: 77 mcg; 1 teaspoon: 400 mcg
haddock, 3 ounces: 104–145 mcg
cod, 3 ounces: 99 mcg
shrimp, 3 ounces: 21–37 mcg
processed fish sticks: 17 mcg per piece
tuna, canned, 3 ounces: 17 mcg
milk, 1 cup: 55-60 mcg
cottage cheese, 1/2 cup: 25–75 mcg
egg, 1 large: 18–29 mcg
turkey breast, cooked, 3 ounces: 34 mcg
ground beef, cooked, 3 ounces: 8 mcg
seaweed, dried, 1 ounce: up to 18,000 mcgIodine deficiency
Because of iodine supplementation, iodine defi-
ciency is not a serious health problem in most indus-
trialized countries, but it is in many developing
countries. Internationally, about 2.2 billion people
are at risk for IDDs. Women who do not get enough
iodine have higher rates of infertility, miscarriages,
pregnancy complications, and low birth weight babies
than women who have adequate iodine intakes. How-
ever, iodine deficiency has its most damaging effects
on the developing fetus.
Iodine deficiency is the leading cause of prevent-
able mental retardation worldwide. Children born to
iodine-deficient mothers have a condition called cre-
tinism. Cretinism involves severe and permanent brain
damage. These children have mental retardation and
developmental disorders such as deafness, mutism,
and inability to control muscle movements. Iodine
deficiency in newborns and infants also results in
abnormal brain development and retardation.
The most visible sign of iodine deficiency in chil-
dren, adolescents, and adults is the development of a
goiter. A goiter is a lump near the throat that signals
an enlarged thyroid. When not enough iodine is avail-
able, the thyroid grows larger in a futile attempt to
make more thyroid hormone. In adults hard lumps
may form inside the goiter. When iodine deficiency is
pronounced enough for a goiter to develop, memory
and language skills decline. In children IQ may be
affected. Some of these effects can be reversed in chil-
dren, but not adults, by increasing iodine intake. In
adults with goiter, increasing iodine intake may send
the thyroid into overdrive, causing it to produce tooIodine