Summary
According to the World Health Organization,
iodine deficiencies during pregnancy are the
greatest single cause of preventable mental impairment in children. However, societal trends are leading away
from reliable sources of dietary iodine. In recent decades, nutritional surveys show
declining levels of iodine in the population, particularly among women of
child-bearing age. We owe it to the
children of the next generation to understand the importance of dietary iodine and provide unborn children with the nutrients they need.
Iodine is a trace nutrient,
measured in micro-grams and necessary for the health of adults and
children. Iodine is especially important
during pregnancy, when dietary iodine requirements increase by 50%, for a
variety of metabolic reasons. Children
born to mothers who are iodine-deficient run the risk of developmental
disorders, mental impairment, and increased risk of autism. Iodine
deficiency during pregnancy causes lower IQs in children by about 10 to 15
points, impaired social development, risk of physical development disorders,
and increased incidence of autism. Children
born to mothers who are only mildly iodine deficient have an increased risk of
lower IQs and autism-spectrum disorders.
Iodine consumption in the
United States and Britain has been decreasing for 40 years. Iodine consumption has fallen due to
increasing use of prepared foods, restaurant foods, and sea-salt, which do not
contain iodized salt. In the United States and Britain, medical
surveys show that women of child-bearing age and pregnant women have lower
levels of iodine than the general population and are often iodine
deficient.
Salt and Forgotten Knowledge
In 1924, the United States began one of the simplest
and most effective public health measures ever taken. Health authorities encouraged salt
manufacturers to make and sell iodized table salt.
The program was spectacularly successful. Iodized salt reduced the occurrence of
thyroid disorders across the northern United States and eliminated severe
mental impairment due to iodine deficiency.
Later studies showed that the program raised the average IQ of citizens
living in iodine-deficient areas by about 15 points. After that, iodized salt became the standard
in American homes. For nearly a century,
health issues related to iodine deficiency were regarded as a solved problem,
until both the problem and the solution became forgotten knowledge.
According to the World Health Organization, iodine
deficiency is the single most important preventable cause of brain damage in
the world. Since the 1970s, the United
Nations has worked to provide iodized salt or other iodine supplements to
populations worldwide. WHO has said
that ending iodine deficiency would be on a par with eliminating smallpox. Iodine deficiency is a really big problem
where populations do not receive supplemental dietary iodine.
Today, the effective use of iodine supplements is
declining in the United States and Britain, and iodine deficiency is becoming common,
particularly among women of child-bearing age and pregnant women. The known consequences of mental impairment
and thyroid problems in their children are likely to follow.
All public health authorities agree that iodine is an essential nutrient, especially during pregnancy. But there is controversy about the delivery method for iodine. For every means of obtaining iodine, there is someone offering caution or opposing its use. Many doctors recommend eliminating the use of table salt. There is some evidence that iodine supplements in pills are poorly absorbed or ineffective, and some health authorities recommend severe limits on the consumption of fish due to the fear of mercury contamination. This issue needs attention from public health authorities, and consensus on the best way to obtain dietary iodine.
All public health authorities agree that iodine is an essential nutrient, especially during pregnancy. But there is controversy about the delivery method for iodine. For every means of obtaining iodine, there is someone offering caution or opposing its use. Many doctors recommend eliminating the use of table salt. There is some evidence that iodine supplements in pills are poorly absorbed or ineffective, and some health authorities recommend severe limits on the consumption of fish due to the fear of mercury contamination. This issue needs attention from public health authorities, and consensus on the best way to obtain dietary iodine.
History of
Iodine Supplements in Public Health
We’ve known for over 100 years that iodine is a
necessary micro-nutrient for thyroid function.
The initial program to provide supplemental iodine in salt was intended
to combat thyroid disorders such as goiter.
Goiter was a common disorder before the 1920s, across a broad swath of
the northern United States known as the Goiter Belt. It was also known that supplemental iodine could
prevent the syndrome of cretinism, which is marked by severe mental impairment,
problems with motor coordination and physical deformities. Cretinism is related to iodine-deficient diet
in pregnant women. Programs in the United States and Switzerland in the 1920s
eliminated cretinism in areas of iodine deficiency. For the rest of the twentieth century, iodine
deficiency was considered a solved problem in the United States.
By the 1970s, iodine supplements came to be recognized
as a core part of international aid programs.
Programs to iodize salt or provide other dietary iodine supplements were
implemented in most of the developing world, and today, most of the world has
access to dietary iodine. Still, nearly
two billion people are considered to be at risk for iodine deficiency, and
international aid programs continue to make progress in bringing iodized salt
to iodine-deficient populations.
Recent
Research
Research over the past two decades has reaffirmed the
importance of dietary iodine supplements.
A landmark study in Britain, published in 2013 in the medical journal
Lancet, shows that even a mild iodine deficiency during pregnancy is a risk to
a developing fetus. The study was careful and comprehensive;
accounting for 21 potentially confounding variables, such as socio-economic
status. Children of mothers with
mild-to-moderate iodine deficiency were followed until age 8. Children of mothers with iodine deficiency
during pregnancy were more likely to be in the bottom 25% in terms of IQ. Impairment was most evident in verbal IQ
and reading proficiency. The degree of
impairment was proportional to the degree of iodine deficiency; the greatest
mental impairment occurred in children whose mothers had the greatest iodine
deficiency.
A meta-analysis of about three dozen studies of iodine
supplementation found that prenatal supplementation showed clear benefits in
terms of the mental and educational development of children. Iodine supplementation after birth showed
only marginal improvements. A typical
study in the review concluded that for the timing of supplementation during
pregnancy, “earlier is better” as a rule.
The meta-analysis is published on a blog without the process of peer
review, but nevertheless provides a good overview of recent scientific
literature on the topic.
Iodine
Deficiency in Britain and the United States
There is no direct way of measuring the iodine
sufficiency in an individual. Iodine
sufficiency is generally measured in terms of urinary iodine, which fluctuates
daily according to iodine consumption.
Still, the urinary iodine test provides a means to statistically measure
iodine consumption across a population and determine whether a group is
receiving sufficient iodine or not.
Five recent studies across the UK have shown iodine
deficiencies in pregnant women, particularly in the first trimester of
pregnancy, which is believed to be the most important. More than 60 percent of the pregnant women
participating in the Lancet study were iodine deficient.
In the United States, measured levels of iodine in the
population have been falling since the 1970s.
From the 1970s to the 1990s, the measured level of iodine fell by
half. In general, iodine levels in the
United States population are considered adequate, but iodine levels in women of
childbearing age are consistently lower than the general population, a trend
that has persisted since 2001.
Dietary
Iodine Requirements
Most foods are low in dietary iodine. The exceptions are seafood, dairy products,
eggs, some vegetables grown in iodine-rich soil, and iodized salt. The recommended daily intake of iodine for
most adults is 150 micrograms per day.
This is roughly the amount that you can receive by eating one serving of
baked cod, and one cup of milk. Other
species of fish, such as tuna and salmon, are not as iodine-rich as cod,
however. Alternatively, you might eat
one cup of yogurt, two eggs, and a quarter-teaspoon of iodized salt.
The recommended amount of dietary iodine consumption
for pregnant women is rising even as the measured level of iodine in the
general population is falling. In 2001,
the World Health Organization recommended a diet containing 200 micrograms per
day, but in 2007, WHO increased its recommendation of daily intake to 250 micrograms of iodine per day for pregnant women.
Current standards of the U.S. National Institutes of Health recommend
220 micrograms per day for pregnant women, and 290 micrograms for lactating
(breast-feeding) women. This is
roughly equivalent to eating two servings of cod plus a cup of milk every day.
Alternatively, a pregnant woman could reach the recommended iodine intake with
two cups of yogurt, one serving of fish sticks, one serving of shrimp, and one
can of tuna every day.
In short,
sourcing iodine from diet alone would require a pregnant woman to eat
unrealistically large amounts of fish, according to John Lazarus,
specialist in hormone disorders and chair of the UK Iodine Group, and Professor
Emeritus of Cardiff University.
Rising Iodine Deficiency
Colorful bottles of sea-salt line the shelves of
upscale groceries and gourmet shops.
Artisan crafted, in specialty glass with names from distant exotic
places, they promise pure and natural ingredients. But by omission, these products may
contribute to a degradation of the mental acuity and health of the next
generation.
Why is iodine deficiency rising in the United States
and Britain? There are several reasons
which are obvious, and possibly others that are not so obvious.
1)
The main reason that iodine levels have been
falling for 40 years is decreased preparation of food at home, with the
consequent lower consumption of iodized table salt. Restaurant foods and prepared
foods contain a lot of salt, but they do not contain iodized salt. By some estimates, restaurant and prepared
foods now account for 70% to 90% of Americans’ salt consumption, but this does
not contribute to dietary iodine.
2)
Another reason for declining iodine sufficiency
is the rising prevalence of vegetarian, vegan, and the newer fad of paleo-diet.
Vegetarians and vegans are particularly at risk of iodine deficiency;
a 2001 study found that vegans in America are generally iodine deficient.
3)
Sea salt
and kosher salt do not contain significant amounts of iodine. Among Americans who are not vegetarian, there
is increasing use of sea salt, kosher salt, and other non-iodized salt, due to increasing
public belief in natural foods and suspicion of additives. Currently, about 12 percent of table salt
sold in America is sea salt.
4)
The medical community is complicit in the broad
declines in iodine sufficiency. Medical
authorities, focused on cardiac health, blood pressure, and fluid retention
issues during pregnancy, declared a “War
on Salt” about thirty years ago.
Even today, official advice letters encourage pregnant mothers to “put
away the salt shaker”, without concern or comment about pre-natal health or
iodine deficiency.
5)
There is a possible decrease in the use of
iodine disinfectants in the dairy industry, which might lead to a decreased
concentration of incidental iodine in milk products.
Sources of
Dietary Iodine
Seaweed is by far the richest source of dietary
iodine. But the amount of iodine in a
bit of seaweed varies widely and up to dangerous levels. According to the NIH, a gram of seaweed can
contain between 16 and 2984 micrograms of iodine. Other references indicate that ¼ gram of
seaweed can contain 4600 micrograms of iodine.
Since 1100 micrograms is considered the safe upper limit for daily
iodine consumption, routine consumption of seaweed as an iodine source is not
recommended.
Seafood is by far the best general source of iodine,
including fish, shrimp, and shellfish.
Salt-water white fish such as cod are the best sources, while tuna and
salmon are less concentrated. Dairy
products, particularly from cows eating iodine-fortified feed, can be a good
source of iodine. Eggs and meat can
contribute to iodine sufficiency, but are likely to be inadequate without
supplementation.
Organic milk is known to be about 40% lower in iodine
content than regular milk.
A few select sources of iodine are given in the table
below, from the National Institutes of Health.
Food
|
Approximate
Micrograms (mcg) per serving |
Percent DV*
|
Seaweed, whole or sheet, 1 g
|
16 to 2,984
|
11% to 1,989%
|
Cod, baked, 3 ounces
|
99
|
66%
|
Yogurt, plain, low-fat, 1 cup
|
75
|
50%
|
Iodized salt, 1.5 g (approx. 1/4 teaspoon)
|
71
|
47%
|
Milk, reduced fat, 1 cup
|
56
|
37%
|
Fish sticks, 3 ounces
|
54
|
36%
|
Bread, white, enriched, 2 slices
|
45
|
30%
|
Fruit cocktail in heavy syrup, canned, 1/2 cup
|
42
|
28%
|
Shrimp, 3 ounces
|
35
|
23%
|
Ice cream, chocolate, 1/2 cup
|
30
|
20%
|
Macaroni, enriched, boiled, 1 cup
|
27
|
18%
|
Egg, 1 large
|
24
|
16%
|
Tuna, canned in oil, drained, 3 ounces
|
17
|
11%
|
Table from the National Institutes of
Health
Supplemental
Dietary Iodine
In the United States, iodized salt has been the primary
means of providing supplementary iodine to the population. In Great Britain, supplementary iodine is
provided in grain and in milk products, through the introduction of
supplemental iodine in cattle feed. In
both countries, incidental iodine supplementation occurred through the use of
iodine disinfectants in the dairy process.
Maternal vitamin supplements are the most certain
source of supplemental iodine for pregnant women. Maternal vitamins SHOULD BE TAKEN WITH GREAT
CARE, and only a single daily dose of vitamins taken, because some vitamins can
become toxic or damaging to the unborn baby at higher levels than the dosage
provided. The vitamin should be checked for iodine
content. Despite the known importance of
iodine during pregnancy, as of 2011, only about 50% of maternal vitamins
contained supplemental iodine. The usual
dosage is about 150 micrograms, leaving the mother to acquire about 100
micrograms of iodine daily from other dietary sources (e.g. two eggs and a cup
of yogurt, or fish sticks and a cup of milk).
A single study found no benefit from supplementary iodine
in maternal vitamins. The study did not
follow children past one year of age, and may have been too short to find
meaningful results. The study may also
indicate that not all means of iodine supplementation are equal. In contrast to vitamin supplements, iodized
salt has a long-established track record in effectively providing iodine
supplementation during pregnancy and early childhood.
Dietary
Fish
When I was a child, children would tell each other that
fish was “brain food”. It turns out that
the children’s myth is correct. Studies
from around the world show that eating fish at any point in life can improve IQ
and memory. But eating fish is
particularly important during pregnancy.
Numerous studies have found that mothers who regularly eat fish during
pregnancy will have children with higher IQs and a lower risk of autism.
Photo Credit El Segundo Fish Company. Used without permission, but with thanks.
The mental benefits of eating fish are generally
attributed to omega-3 fatty acids. But
some researchers also noted that fish represent an excellent source of iodine,
which is also known to provide benefits during pregnancy and afterwards.
It is important to note that health authorities are
divided on the recommended amount of fish to eat. United States’ dietary guidelines recommend
that pregnant women consume no more than 12 ounces of fish per week, due to
concerns about mercury in fish. European
guidelines recommend up to 21 ounces (600 grams) of fish per week.
A recent study in Spain found that every 10 grams of
increased fish consumption was correlated with higher IQs. Researchers also found decreased incidence of
autism in children from mothers who ate the most fish. The study found that even at 21 ounces of
fish per week, there was no indication of mercury having a negative effect on
child development. An earlier study in
Britain also found that consuming fish during pregnancy led to high IQs among
children. Researchers found beneficial
effects for children from mothers who ate more than 12 ounces of fish per
week. The researchers in this study
found no protection against adverse outcomes among mothers who ate less than 12
ounces of fish per week. According to
the authors, the risk from inadequate nutrients was greater than the risk of
exposure to trace contaminants due to eating fish.
The conclusion should be that expectant mothers should
regularly include fish as part of a pregnancy diet, to increase the mental
abilities and social development of their children, while decreasing the risk
of autism-spectrum disorders. Mothers
should avoid the kinds of fish which are likely to contain unhealthy concentrations of
mercury. Swordfish, shark, king
mackerel, ahi tuna and albacore tuna should be avoided. In general, smaller fish contain less mercury
than large fish. Short-lived fish like
salmon, cod, and pollack contain less mercury than long-lived fish like rockfish.
Dietary
Advice for Pregnancy
Dietary advice of any kind
is maddening; dietary advice for pregnancy is especially so.
Any woman planning to become
pregnant, or who might become pregnant, should consult with a doctor about diet
and lifestyle choices in order to have a healthy baby. This post is not intended to take the place
of that advice, but rather to raise the awareness of nutrition requirements, in
particular the need for iodine and folic acid.
There are a couple of important points to put first.
1)
A
developing baby needs a lot of protein – 70 to 100 grams a day. In a practical sense, it is very difficult
to obtain that much protein, and the necessary variety of amino acids, without
eating meat. Many reference sites
recommend 3 servings of meat, poultry, eggs, fish or seafood per day. Other sources, including dairy, legumes,
nuts, and soy are also important.
2)
A dietary supplement designed for pregnancy is
generally recommended. It is important
to only use one supplement. High
doses of some vitamins, particularly vitamin A, are toxic, and can lead to
birth defects. The dietary supplement
should include iodine and folic acid.
3)
Regular consumption of fish, particularly
salt-water fish, provides natural iodine, omega-3 fatty acids, and
protein. Avoid species associated with
high mercury content, and eat plenty of fish.
4)
Iodine is
a necessary micro-nutrient in pregnancy and early childhood. For nearly a century, it has been known that
serious iodine deficiency during pregnancy can cause life-long mental
impairment. Recent research in Britain
now shows that even mild to moderate iodine deficiencies also causes
significant mental impairment. Further,
surveys in Britain and the United States show that many pregnant women and
women of child-bearing age are deficient in iodine. Iodized salt has a clear track record in effectively
delivering dietary iodine; ¼ to ½ teaspoon of salt daily is enough.
5)
Folic acid is another very important nutrient
during pregnancy. Folic acid is found in “leafy green
vegetables” and various artificially fortified foods. Deficiency in folic acid is the cause of
many, if not most, birth defects, including spina bifida. Like
iodine, it is difficult to obtain sufficient folic acid through diet
alone. To obtain the required amount of
folic acid from one of the richest sources, it would be necessary to eat five cups of broccoli a day. Although there is
evidence that synthetic folic acid is slow to convert to useful forms in the
body, folic acid supplements have been shown to reduce birth defects such as
spina bifida, cleft palates, congenital heart defects, limb defects and urinary
tract abnormalities. Many breads and
cereals are also good sources of supplemental folic acid.
----
Iodized Salt References
Iodine in Public Health
Iodization of salt may be the simplest and most cost-effect public
health measure available.
Iodine deficiency affects two billion people, and is the leading cause
of intellectual and developmental disabilities.
Residents of the northern United States were subject to widespread
iodine deficiency prior to the 1920s.
After the introduction of iodized salt, IQs in the region increased by
15 points on average.
Iodized Salt in 1914 raised IQ in iodine across most of the northern
United States by 15 points, according to military recruiting records. The sudden introduction of iodized salt
resulted in about 10,000 thyroid-related deaths over several decades.
The World Health Organization has said that ending iodine deficiency
would be on a par with the elimination of smallpox.
Iodine deficiency can lead to a 13 point reduction in IQ.
Iodine Global Network, an NGO dedicated to improving iodine
nutrition worldwide.
Nicholas Kristof on World Iodine supplementation.
Date: 2001
WHO, UNICEF, and ICCIDD (4) recommend that the daily intake of iodine
should be as follows: n 90 µg for preschool children (0 to 59 months); n 120 µg
for schoolchildren (6 to 12 years); n 150 µg for adults (above 12 years); and n
200 µg for pregnant and lactating women.
Iodine in Pregnancy: Is Salt Iodization
Enough?
Iodine deficiency affects
more than 2.2 billion individuals worldwide (38% of the world’s population).
Decreases in maternal T4 associated
with even mild iodine deficiency may have adverse effects on the cognitive
function of offspring (1,2), and iodine deficiency remains the leading cause of
preventable mental retardation worldwide. It has recently been suggested that
mild iodine deficiency may also be associated with attention-deficit and
hyperactivity disorders in offspring (3).
WHO optimal range of UI is
150 – 259 mg/l. WHO recommendation for
dietary iodine is 200 – 300 mg/day (2007).
Endocrine society recommends dietary iodine intake of 220 mg/day.
American Thyroid Association
recommends supplements of 150 mg/d for women during pregnancy and lactation.
An equivalence between
dietary iodine and urinary iodine can be established. The level of urinary iodine, in micrograms of
iodine per liter of creatine, is about two-thirds of dietary iodine consumption
per day. For instance, dietary iodine
of 150 micrograms/day will correspond with UI of 100 micrograms/liter.
The association of iodine deficiency with goiter was made in the
mid-to-late 1800s.
Urinary iodine levels declined 50% from the 1970s to the 1990s, and has
since stabilized (article date 2012).
Iodized salt introduction in Switzerland in 1922 resulted in a decrease
in goiter and the elimination of cretinism.
Maps and graphs.
Iodine deficiency during pregnancy typically results in mental
handicaps, with reductions of 10 to 15 IQ points.
Iodine supplementation improved cognitive and motor performance of
iodine deficient children.
Anecdotal evidence from Chinese village
Iodine Deficiency
Effect of inadequate iodine status in UK pregnant
women on cognitive outcomes in their children: results from the Avon
Longitudinal Study of Parents and Children (ALSPAC), Bath et al, 2013.
Iodine deficiency in pregnancy was correlated to deficits in verbal IQ,
reading accuracy and reading comprehension at age 8. The deeper the iodine deficiency during
pregnancy, the worse the children’s reading and IQ scores were at age 8.
Children of women in the group with less than 150 mg/l of
iodine/creatinine were more likely to score in the bottom quartile in verbal IQ
and reading proficiency.
The study took into account and corrected for 21 potentially
confounding variables.
According to the WHO, a median urinary iodine concentration of 150–249
mcg/L indicates adequate iodine nutrition during pregnancy, while values less
than 150 mcg/L are considered insufficient [3,7]. Analyses of NHANES datasets
covering time periods from 2001 to 2008 indicate that a substantial portion of
pregnant women in the United States are iodine insufficient. Median urinary
iodine concentrations for pregnant women participating in NHANES surveys were
181 mcg/L in 2003–2004 [21] and 153 mcg/L in 2001–2006 [26], and only 125 mcg/L
in 2005–2008 [25]. Further, 56.9% of pregnant women surveyed during 2005–2008
had a median urinary iodine concentration <150 mcg/L [25]. In a study
published in 2004, the median urinary iodine concentration of 100 healthy
pregnant women in Boston was 149 mcg/L and 49% of the women had values below
the WHO cutoff for sufficiency [27]
Pregnant women who do not consume dairy products are particularly at
risk for iodine deficiency.
According to NHANES 2001–2006 data, pregnant women who consumed no
dairy products in the previous 24 hours had a median urinary iodine
concentration of only 100 mcg/L, compared with 163 mcg/L among consumers of
dairy [26].
Chronic iodine deficiency in children reduces IQ by 12 to 13.5
points. Mild to moderate maternal
iodine deficiency is associated with increased risk of hyperactive attention
deficit disorder.
Up to 60% of mothers in one study had iodine deficiency; their children
had greater risk of low IQs.
Five recent studies of pregnant women in Britain showed substantial
iodine deficiency.
Professor John Lazarus, Chair of the UK Iodine Group and a
specialist in hormone disorders, Sourcing
it from the diet alone “would require a woman to eat unrealistically large
amounts of fish.
Iodine Status of the U.S.
Population, National Health and Nutrition Examination Survey, 2005–2006 and
2007–2008
Kathleen L. Caldwell, Amir Makhmudov,
Elizabeth Ely, Robert L. Jones, and Richard Y. Wang. Thyroid. April 2011,
21(4): 419-427. doi:10.1089/thy.2010.0077.
The median U.S population UI was 164
micrograms/liter in 2005 – 2008.
However, the median UI of all pregnant women surveyed was 125 mg/l. 57% of pregnant woman had UI levels under
150 mg/l. UI levels were lower in the
black population.
The UI concentrations were consistently lower in women of childbearing
age compared with
the general population, a relationship that has been observed since 2001. In the general population, UI levels were
the lowest in the age group of 20 – 29.
UI levels were also very low in the black population.
The median UI concentration for the general U.S. population in NHANES
2009–2010 was significantly lower than the levels found during NHANES
2007–2008.
The Effects of Iodine Deficiency
in Pregnancy and Infancy, M. B. Zimmermann, 2012, Paediatric and Perinatal
Epidmilogy, doi: 10.1111/j.1365-3016.2012.01275.x
Iodine supplementation eliminates new cases of cretinism, increases
birthweight, reduces rates of perinatal and infant mortality, and generally
increases developmental scores in children by 10%-20%. Mild maternal iodine deficiency can cause
thyroid dysfunction, but whether it impairs IQ is unknown. In nearly all areas with iodine deficiency,
salt iodisation is the most cost-effective way to deliver iodine and improve
maternal and infant health.
Don’t depend on processed foods for iodine: the salt used to prepare
them is not iodized. Iodine intakes in
the United States have declined from about 250 micrograms per day to about 157
mg per day. [Figures also cited in the Salt Institute Paper, also without dates.] Pregnant women need to consume more for the
health of their babies. Consumption of
up to 1100 mg is considered safe for adults and children over the age of 4.
Seaweed is the most concentrated source of dietary iodine. Shellfish are a large source, followed by
certain fish. Eggs and milk can be minor
sources of iodine.
Iodine deficiency in the United States is on the rise. Levels of urinary iodine have fallen by half
since the 1970s. Although there is a lot
of salt in pre-packaged foods, the salt in these foods is not necessarily
fortified with iodine. There are
indications that the average pregnant woman in the United States has
substandard iodine nutrition. This is
absolutely a concern, because iodine is necessary for proper development for
the development of the brain and nervous system.
Iodine is necessary for proper thyroid function.
A 2011 study found that vegans in America are generally iodine
deficient.
Recent research has shown mild iodine deficiency in schoolgirls and
pregnant women. There is now concern that many adult women may not be getting
enough iodine, particularly in pregnancy
Adults need 150 micrograms of iodine per day.
Pregnant and Breastfeeding women need 250 micrograms of iodine each
day.
Organic milk has a 40% lower iodine content than conventional milk.
Adult intakes should not exceed 600 micrograms per day.
Vegetarians and vegans are particularly at risk of iodine deficiency.
It can be difficult to meet the higher recommendations for iodine
during pregnancy, especially if you do not consume rich sources of iodine.
Organic milk
contains 30% less iodine than standard milk.
“Iodine
deficiency ought to be a health problem from the past. But unless this
situation is carefully monitored, we risk sleepwalking into a new health crisis
in the 21st century”
About iodine deficiency
CDC article summarizing salt sales in the United States. Data summarized in the next reference.
Summary of US iodized and non-iodized table salt
sales. Only 57 of 1117 brands are
iodized, but represent 53% of sales.
Salt blends (seasoned salt) is not iodized. Only about 12% of American salt consumption
comes from table salt or cooking; 88% of salt consumption is from non-iodized
salt in pre-packaged or restaurant foods.
Saltworks, incorporated doubled sales from $5 million to $10 million
from 2006 to 2007.
The 2006 figure represented 10 million pounds of salt.
A website for a commercial seasalt provider.
Harvard medical letter recommends against getting your iodine from
salt. They recommend sea food, milk
products, and “vegetables raised in iodine-rich soil”. Not that the consumer is going to know what
kind of soil their vegetables were raised in.
To get all of your iodine from salt, you would need a half-teaspoon of
iodized salt every day.
Americans receive 70% to 90% of their sodium from restaurants,
processed and prepared foods which do not contain iodized salt.
Iodized Salt has a shelf life of about 5 years. According a study at the University of
Texas, about half of the iodized salt prepared in this country lacks sufficient
iodine to meet daily requirements.
The combination of a Paleo diet and the modern food environment can
unintentionally create a dangerously low dietary iodine intake.
Urinary levels of iodine have declined for 40 years.
Pregnant women are often mildly iodine deficient, even in the United
States.
The top three iodine sources in the modern diet are artificial.
Claims that milk contains iodine only because of the iodine used as a
disinfectant on cows udders and on milk containers.
Columnist Suzy Cohen from the South Florida Sun-Sentinel makes many important points about dietary
iodine. However, she advocates “natural”
iodine, rather than iodized salt. Cohen
doesn’t understand that humans rarely consume elemental iodine, and that most
forms of consumable iodine are in molecules, in the form of iodide or iodate.
Paleo Slow Cooking, Molly Pearl, 2014
The book Paleo Slow Cooking advocates replacing iodized salt with
kosher salt or sea salt.
Thyroid Disease, Dr. Alan Christianson, Hy Bender, 2011
Fast food restaurants, processed and prepared foods do not use iodized
salt.
Sources of Iodine
Age
|
Male
|
Female
|
Pregnancy
|
Lactation
|
Birth to 6 months
|
110 mcg*
|
110 mcg*
|
||
7–12 months
|
130 mcg*
|
130 mcg*
|
||
1–3 years
|
90 mcg
|
90 mcg
|
||
4–8 years
|
90 mcg
|
90 mcg
|
||
9–13 years
|
120 mcg
|
120 mcg
|
||
14–18 years
|
150 mcg
|
150 mcg
|
220 mcg
|
290 mcg
|
19+ years
|
150 mcg
|
150 mcg
|
220 mcg
|
290 mcg
|
* Adequate Intake (AI)
The World Health
Organization (WHO), United Nations Children's Fund (UNICEF), and the
International Council for the Control of Iodine Deficiency Disorders (ICCIDD)
recommend a slightly higher iodine intake for pregnant women of 250 mcg per day
[3,7].
Food
|
Approximate
Micrograms (mcg) per serving |
Percent DV*
|
||
Seaweed, whole or sheet, 1 g
|
16 to 2,984
|
11% to 1,989%
|
||
Cod, baked, 3 ounces
|
99
|
66%
|
||
Yogurt, plain, low-fat, 1 cup
|
75
|
50%
|
||
Iodized salt, 1.5 g (approx. 1/4 teaspoon)
|
71
|
47%
|
||
Milk, reduced fat, 1 cup
|
56
|
37%
|
||
Fish sticks, 3 ounces
|
54
|
36%
|
||
Bread, white, enriched, 2 slices
|
45
|
30%
|
||
Fruit cocktail in heavy syrup, canned, 1/2 cup
|
42
|
28%
|
||
Shrimp, 3 ounces
|
35
|
23%
|
||
Ice cream, chocolate, 1/2 cup
|
30
|
20%
|
||
Macaroni, enriched, boiled, 1 cup
|
27
|
18%
|
||
Egg, 1 large
|
24
|
16%
|
||
Tuna, canned in oil, drained, 3 ounces
|
17
|
11%
|
||
Corn, cream style, canned, 1/2 cup
|
14
|
9%
|
||
Prunes, dried, 5 prunes
|
13
|
9%
|
||
Cheese, cheddar, 1 ounce
|
12
|
8%
|
||
Raisin bran cereal, 1 cup
|
11
|
7%
|
||
Lima beans, mature, boiled, 1/2 cup
|
8
|
5%
|
||
Apple juice, 1 cup
|
7
|
5%
|
||
Green peas, frozen, boiled, 1/2 cup
|
3
|
2%
|
||
Banana, 1 medium
|
3
|
2%
|
||
Age
|
Male
|
Female
|
Pregnancy
|
Lactation
|
Birth to 6 months
|
Not possible to establish*
|
Not possible to establish*
|
||
7–12 months
|
Not possible to establish*
|
Not possible to establish*
|
||
1–3 years
|
200 mcg
|
200 mcg
|
||
4–8 years
|
300 mcg
|
300 mcg
|
||
9–13 years
|
600 mcg
|
600 mcg
|
||
14–18 years
|
900 mcg
|
900 mcg
|
900 mcg
|
900 mcg
|
19+ years
|
1,100 mcg
|
1,100 mcg
|
1,100 mcg
|
1,100 mcg
|
Top 10 Iodine Rich Foods List
1) Dried seaweed
¼ oz: 4500 mcg (over 100% DV)
¼ oz: 4500 mcg (over 100% DV)
2) Cod fish
3 oz: 99 mcg (66% DV)
3 oz: 99 mcg (66% DV)
3) Yogurt
1 cup: 87 mcg (58% DV)
1 cup: 87 mcg (58% DV)
4) Turkey breast
3 oz: 34 mcg (23% DV)
3 oz: 34 mcg (23% DV)
5) Navy beans
½ cup: 32 mcg (21% DV)
½ cup: 32 mcg (21% DV)
6) Tuna
3 oz: 17 mcg (11% DV)
3 oz: 17 mcg (11% DV)
7) Eggs
1 large: 12 mcg (8% DV)
1 large: 12 mcg (8% DV)
8) Baked potato
1 medium: 60 mcg (40% DV)
1 medium: 60 mcg (40% DV)
9) Strawberries
1 cup: 13 mcg (8.6% DV)
1 cup: 13 mcg (8.6% DV)
10) Cranberries
1 oz 90 mcg (60% DV)
1 oz 90 mcg (60% DV)
Low Prenatal Iodine May Affect
Child's Brain Development
Mothers with deficiency had kids
with lower IQs and reading ability, researchers say
1 cup of yogurt contains 75 micrograms of iodine; 1 cup of milk
contains 56 micrograms of iodine.
3 ounces of baked cod contains 99 micrograms of iodine.
Recommendations for Iodine Consumption
Iodine has not been part of the public health agenda in the UK for the
past 50 years; iodine requirements for pregnancy and lactation are outdated,
population monitoring has been absent, and advice to pregnant women has not
included information about iodine intake.
WHO guidelines recommend iodine intake for pregnant women of 250
micrograms per day.
Long and very informative technical paper by UNICEF and WHO, 2007. Recommended daily consumption levels and
supplements included. Recommendation for
pregnant and lactating women of 250 micrograms/day.
Dietary Fish
Study in Spain, 2016, showed that eating three to
four servings of fish per day during pregnancy resulted in higher IQs in
offspring. No negative effects from
mercury were noted. Higher consumption
of fish also correlated with a consistent reduction of autism-spectrum
disorders in children.
The article cited a 2004 study from Denmark, that
noted negative effects from high fish consumption during pregnancy, due to
mercury contamination. “Many other
studies” have linked eating fish during pregnancy with better outcomes in
children.
During Pregnancy, Consuming Fish Improves Offspring's Cognitive
Development And Prosocial Conduct
University of Grenada study showed that eating fish during pregnancy
raises the IQ of offspring. 2012
Higher IQ in seniors (age 64) correlated with fish-oil consumption.
Consumption of fish related to high IQs among teenagers in India.
By Stephen Daniells,
16-Feb-2007
Eating more than 340 grams of
omega-3-rich seafood per week during pregnancy was associated with higher
verbal intelligence quotient (IQ) scores in the children, says a new study.
The study found that fish consumption
of less than 340 grams (12 ounces, or 4 servings) per week did not protect
children from adverse outcomes.
Improvements in child development were recorded from mothers who ate
more than 340 grams (12 ounces) of fish per week. According to the researchers, the risk from
the loss of nutrients was greater than the risk of exposure to trace
contaminants in 340 grams (21 ounces) of seafood eaten weekly.
Spanish study, 2016, found that consumption of fish during pregnancy
increased the IQ of children, up to 600 grams (21 ounces, or seven servings) of
fish per week. No further gains were
noted beyond that level. European
guidelines allow up to 600 grams of fish consumption per week; by comparison,
U.S. guidelines recommend no more than 340 grams (12 ounces, or four servings)
of fish per week. Each 10 gram increase
in fish consumption was tied to higher IQ scores at age 5. Higher amounts of fish consumption correlated
with lower incidence of autism.
El Segundo Fish Company
Benefits of eating fish, with photo credit.
Iodine Supplements
Supplementation by iodine in the form of salt, water, or oil can raise
IQ scores in deficient areas by up to 13 points. Cooking may reduce iodine content in iodized
salt. The window for iodine
intervention may close rapidly during pregnancy, and be closed post-birth.
Meta-analysis of many studies seems to show little improvement in
iodine-deficient children. Studies of
pregnancy support the idea that “earlier is better” for iodine supplementation.
57 out of 1117 salt products were iodized. Iodized salt represents 53% of the total
volume of salt sales in the United States (2015). A historical estimate
Adequate intake of iodine, a
trace element, plays a key role in regulating human growth, development, and
metabolic functions. It is estimated that, worldwide in 2011, 1.88 billion
people were iodine deficient [1,2]. Iodine deficiency can result in goiter, neurocognitive
impairment, hyperthyroidism, and hypothyroidism [3]. During pregnancy, severe iodine deficiency can cause
cretinism, congenital anomalies, and increased neonatal and infant mortality [2], with recent evidence from observational studies suggesting
mild to moderate deficiency during pregnancy can lead to reduced IQ and
educational achievement among offspring [4,5]. While iodine status is sufficient for most Americans,
certain subsets of the population, including pregnant women, may be at risk for
mild to moderate iodine deficiency [6,7,8]. Iodizing salt is a global public health strategy for
addressing iodine deficiency [9], yet limited data exist on the proportion of salt that is
iodized in the United States.
“IDD is the single greatest cause of
preventable mental retardation. Severe deficiencies cause cretinism, stillbirth
and miscarriage. But even mild deficiency can significantly affect the learning
ability of populations. Scientific evidence shows alarming effects of IDD. Even
a moderate deficiency, especially in pregnant women and infants, lowers their
intelligence by 10 to 15 IQ points, with incalculable damage to social and
economic development of nations and communities. Today over 1 billion people in
the world suffer from iodine deficiency, and 38 million babies born every year
are not protected from brain damage due to IDD. These 38 millions, or nearly 30
percent of the world’s newborns, come from families that are the least
educated, most isolated and economically disadvantaged. The mark of a civilized
society is how well it takes care of its most vulnerable and deprived
communities. If we continue to fail to reach these newborns, we will be
consigning them to an inter-generational cycle of poverty and injustice.”
Salt producers are a key partner in
combating Iodine Deficiency Disorders (IDD) today throughout the world. Many
people erroneously assume that because salt iodization was first implemented
nearly a century ago, that the problem no longer exists. Tragically, that’s
wrong. In 1990, only about 20% of the world’s households had access to iodized
salt and were protected against Iodine Deficiency Disorders. After a major
push, access now exceeds 70%.
Average Iodine intakes have declined
from over 250 micrograms per day to 157 micrograms per day. Health authorities recommend 150 micrograms
per day for adults, particularly for expectant mothers.
Over 1 billion people in the world suffer from iodine deficiency, and
38 million babies a year, or about 30 percent of the world’s newborns, are not
protected from iodine deficiency. In
1990, only 20% of the world’s households had access to iodized salt, but
currently iodized salt is accessible to 70% of households.
Salt used in processed foods are not iodized.
Iodized salt is prepared by spraying a solution of potassium iodide on
salt, in a conveyor belt process.
Treated salt contains 0.002% to 0.004%, or 2 to 4 parts potassium iodide
per 100,000 parts salt.
Iodine deficiency impairs fetal brain development, and imposes a
lifetime intellectual deficit equivalent to 10 to 15 IQ points.
Iodine deficiency is the single greatest cause of preventable mental
retardation, and even a moderate deficiency can cause intellectual impairment
of 10 to 15 IQ points.
The first comprehensive survey of iodized salt sales in the United
States was published in April, 2015.
53% of US dietary salt is iodized; figures as reported elsewhere.
American Thyroid Association recommends that pregnant women take a
supplement with at least 150 mg of iodine each day. Pregnant women actually need more iodine, for
a variety of metabolic reasons.
Worldwide, about 2 billion people are iodine-deficient. A National Health and Nutrition survey found
that half of all American pregnant women show levels of iodine below the
recommended level of 150 micrograms.
In 2009, only 51% of pregnancy vitamin supplements contain iodine, and
tested samples showed that the actual dosage of iodine did not match values on
the labeling.
Iodine supplementation in pregnant and
lactating women
Most foods are
relatively low in iodine content. To ensure that everyone has a sufficient
intake of iodine, WHO and UNICEF recommend universal salt iodization as a
global strategy.
Universal salt
iodization is the recommended intervention for preventing and correcting iodine
deficiency; substantial experience has been gained in the last decade in
implementing this strategy and in assessing its impact on iodine deficiency
disorders (IDD). A major achievement is the spectacular reduction of IDD in countries
that have adopted appropriate measures.
This article identifies table salt as the principle source of iodine,
but only discusses thyroid issues, not neurological development.
A survey in Britain found that 84 percent of British women were unaware
of the importance of iodine-rich foods during pregnancy. Only 12 percent were aware of
iodine-specific dietary advice.
Article sounds a cautionary note about artificial iodine supplement,
references the following study.
Paradoxically found that 150 microgram iodine supplements were
associated with decrease in motor skills at age 1.
This article notes in passing that table salt contains iodine, as an
essential nutrient, important to thyroid function, but does not say anything
about neurological development.
Recommended Salt Intake during Pregnancy
Up to a
teaspoon— 2400 milligrams of sodium, or 6 grams of salt, the same for all
adults and pregnant women, except for those with hypertension. 1500 milligrams for people with
hypertension. According to USDA and HHS.
Intake should
be limited to 2400 milligrams of sodium (6 grams, or one teaspoon of salt per
day.) “Take the salt shaker off the
table during pregnancy.”
Institute of
Medicine has set the adequate daily intake of sodium to 1.5 grams, which is the
same for non-pregnant adults – this is equivalent to 3.8 grams of salt per day,
as salt is only 40% sodium. The
tolerable upper limit is 5.8 grams of salt per day.
Folic Acid and Protein
Protein and protein sources.
Wonder bread contains 9 of the essential vitamins and minerals needed
for good health and children’s development.
8 percent of riboflavin, 10 percent of vitamin D, thiamine, niacin,
folic acid, zinc, iron, vitamin E, vitamins B6 and B12 and 30 percent of
calcium
Folic acid is necessary during pregnancy. Although there is evidence that synthetic
folic acid is slow to convert to useful forms in the body, folic acid
supplements have been shown to reduce birth defects such as spina bifida, cleft
palates, congenital heart defects, limb defects and urinary tract
abnormalities. It is also a cancer
preventative, and necessary for a number of adult health functions.
Folate deficiency may contribute to low birth weight, as well as other
deficiencies.
Folic acid occurs naturally in leafy green vegetables, fruits, beans
and nuts. Folic acid can also be
obtained from fortified breads and cereals.
Women should consume adequate quantities of folic acid before becoming
pregnant.
You would need to eat 5 cups of broccoli to obtain the minimum daily
requirement for folate, which is generally available in a single bowl of
fortified cereal.
Between 5% to 20% of people have spina bifida occulta (hidden). Although the condition is generally benign,
it may contribute to back pain throughout life.
Folic acid supplementation has been shown to prevent an estimated 1300
cases per year of spina bifida. The
introduction of folic acid supplementation caused a 28% reduction in cases of
anencephaly and spina bifida.
Overt birth defects occur in about one in 33 births, and account for
about 20% of infant deaths.
IN a study in Atlanta from 1978 to 2005, the rate of birth defects was
stable. The incidence of birth defects
was lower among black and Hispanic mothers than among white mothers. The overall incidence of spina bifida and
anencephaly may represent fortification of grains with folic acid and increased
use of folic acid supplements.
