new45_statement.pdf

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NHMRC publiC stateMeNt
jaNuaRy 2010
Iodine Supplementation
for Pregnant and
BreaStfeedIng Women
What is iodine and why do we need it?
I
odine is an essential nutrient that humans need in very small
quantities. A small gland in the neck, known as the thyroid,
uses iodine to produce thyroid hormones.
1
These hormones
are vital to ensure normal development of the brain and nervous
system before birth, in babies and young children.
2,3
For this
reason, it is very important that pregnant and breastfeeding
women get enough iodine.
Humans store iodine in the thyroid.
1
As only small amounts can
be stored, any excess is excreted.
4
How much iodine do pregnant and
breastfeeding women need?
NHMRC and the New Zealand Ministry of Health recommend that
women who are pregnant have 220µg of iodine per day. Women who
are breastfeeding should have 270µg per day.
1
The World Health
Organization (WHO) recommends women who are pregnant or
breastfeeding take a daily oral iodine supplement so that the total
daily intake is 250µg.
5
Pregnant and breastfeeding women need to top
up their dietary iodine intake because of the increased requirements
during pregnancy and breastfeeding and the likelihood that they
won’t get enough from their diet and mandatory fortification.
Recommendations
•
the national Health
and medical research
Council (nHmrC)
recommends that
all women who are
pregnant, breastfeeding or
considering pregnancy, take
an iodine supplement of
150 micrograms (µg)
each day.
thyroid conditions should
seek advice from their
medical practitioner prior
to taking a supplement.
What foods contain iodine?
Most foods in Australia contain only small amounts of iodine, making
it difficult for pregnant and breastfeeding women to get enough
iodine through food alone. The amount of iodine varies greatly based
on factors such as changes in season and processing practices.
Fortified bread, dairy and seafood are the main dietary sources of
iodine in Australia.
•
Women with pre-existing
iodine supplementation: public statement
Why do pregnant and
breastfeeding women need
more iodine than other
population groups?
Humans store iodine in the thyroid. In pregnancy,
the thyroid is particularly active, producing about
50% more thyroid hormones than usual.
3
To produce
enough thyroid hormones to support the mother and
foetus, the mother needs to increase her iodine intake.
If iodine intake is inadequate before pregnancy, the
mother’s stores may run low and be inadequate to
support the unborn baby in later stages of pregnancy.
6
The production rate of thyroid hormone returns to
normal when breastfeeding. However, NHMRC
recommends that breastfeeding women also take
an iodine supplement because breast fed infants are
completely dependent on milk as a source of iodine
and need around 90 to 100µg of iodine per day.
1
Infants use this iodine to build their own reserves
of thyroid hormones.
7,8
NHMRC
When iodine intake falls below recommended levels
the thyroid cannot produce enough thyroid hormones
and a range of iodine deficiency disorders can
occur.
1,15
Iodine deficiency is of particular concern
during pregnancy because abnormal function of the
mother’s thyroid has a negative impact on the nervous
system of the unborn baby, and increases the risk of
infant mortality.
3
Adverse effects on early brain and
nervous system development are generally irreversible
and can have serious implications for mental capacity
in later life.
16
I know bread has recently been
fortified with iodine. do pregnant
and breastfeeding women need a
supplement as well?
Yes. Mandatory fortification is where food
manufacturers are required to add a vitamin or mineral
to a food. Mandatory iodine fortification has been
introduced in Australia and New Zealand as an
initiative to improve public health. Bread made in
Australia, where salt is used, except bread represented
as organic, is now required to contain iodised salt,
instead of non-iodised salt. “Bread” includes not only
bread but also rolls and hamburger buns and other
bread products.
Through mandatory fortification, most of the Australian
population will get enough iodine
17
, meaning women
of child bearing age should enter pregnancy with
adequate iodine intake. However, the extra iodine
available through bread is not enough to meet
the additional needs of pregnancy and during
breastfeeding.
18
Therefore, NHMRC recommends that women who are
pregnant, breastfeeding or considering pregnancy take
an iodine supplement of 150µg each day. Supplements
of 150µg/d of iodine are safe and effective for pregnant
and breastfeeding women.
are pregnant and breastfeeding
women getting enough iodine?
No. The weighted results from the National Iodine
Nutrition Survey suggest the median urinary iodine
concentration in Australia is 96µg/L which, according to
WHO, suggests that the Australian population is mildly
deficient.
9
There are limited studies specific to the iodine
status of pregnant women in Australia, but those
available prior to fortification suggest it was inadequate.
9
Why has this occurred?
Reasons suggested for the
recurrence of iodine deficiency in Australia include
reduced use of iodine-based cleaning products by
the dairy industry and reduced household use of
iodised salt (caused by a gradual increase in
consumption of commercially processed foods
containing non-iodised salt).
10
What happens if pregnant and
breastfeeding women do not get
enough iodine?
The main health concern of mild iodine deficiency
during pregnancy and breastfeeding is its negative
effect on the brain and nervous system of unborn
children and infants, in particular reduced intelligent
quotient (IQ).
11,12,13,14
are iodine supplements safe for
all women?
Women with pre-existing thyroid conditions should
seek advice from their medical practitioner prior to
taking a supplement.
nHmrC Public Statement: Iodine supplementation for pregnant and breastfeeding women
2
iodine supplementation: public statement
Is it possible that by taking an
iodine supplement pregnant and
breastfeeding women will have
too much iodine?
No. In Australia, where the population is only mildly
iodine deficient, taking an iodine supplement at the
recommended dose of 150µg/day will not lead to an
excessive iodine intake. However, monitoring of intake
to ensure levels don’t exceed the recommendation
is included in the mandatory iodine fortification
monitoring framework and will be conducted by
the Australian Institute of Health and Welfare.
NHMRC
mineral supplements include the recommended
amount of iodine and should consider taking
supplements designed specifically for pregnancy
and breastfeeding.
When should women start and
finish taking iodine supplements?
Women should take iodine supplements from the point
of planning pregnancy through the full duration of
pregnancy and breastfeeding. If pregnancy is not
planned, women should start taking an iodine
supplement as soon as possible after finding out
that they are pregnant.
are there any benefits of taking
supplements with more than
150µg iodine?
No. NHMRC recommends supplementation of
150µg/day to ensure that all women who are pregnant,
breastfeeding or considering pregnancy have adequate
iodine status.
As only small amounts of iodine can be stored,
any excess is excreted.
How was this statement
developed?
NHMRC developed this Statement via a review of the
literature and consultation with an expert group.
The review,
Iodine supplementation during pregnancy
and lactation,
is available at www.nhmrc.gov.au.
The evidence supporting this Statement will be
reviewed in time and the Statement revised as
necessary. Members of the expert group were
Professor Katrine Baghurst, Professor Colin Binns,
Professor Peter Davies, Professor Creswell Eastman
and Dr Dorothy Mackerras.
How was the level of
supplementation determined?
The level of supplementation was determined using
data on average iodine intakes post mandatory bread
fortification, based on knowledge that the Australian
population is now classified by WHO as mildly iodine
deficient.
19
,
20
references
1 National Health and Medical Research Council and
New Zealand Ministry of Health (2006).
Nutrient
Reference Values for Australia and New Zealand
including Recommended Dietary Intakes.
Commonwealth of Australia. Available online
at http://www.nhmrc.gov.au.
2 World Health Organization (2004).
Review of iodine
deficiency disorders in the South-East Asia Region:
information document for the fifty-seventh session
of the Regional Committee for South East Asia.
Available online at http://searo.who.int.
3 Zimmermann MB (2009) Iodine deficiency in
pregnancy and the effects of maternal iodine
supplementation on the offspring: a review.
The American Journal of Clinical Nutrition:
89; 668S-672S.
4 Lamberg B (1993) Iodine deficiency disorders and
goitre.
European Journal of Clinical Nutrition:
47; 1–8.
5 World Health Organisation Secretariat (2007) World
Health Organisation Technical Consultation on the
Prevention and control of iodine deficiency.
Public
Health Nutrition:
10; 1606-1611.
are there some iodine supplements
that women who are pregnant,
breastfeeding or planning
pregnancy should not take?
Yes. Women should not take kelp (seaweed)
supplements or kelp based products because they
contain varying levels of iodine
21
and may be
contaminated with heavy metals such as mercury.
In addition, a survey of 15 prenatal supplements
available in Australia found iodine contents of
between 150 and 270µg, with one leading brand
containing no iodine.
22
Pregnant and breastfeeding
women are advised to check that their vitamin and
nHmrC Public Statement: Iodine supplementation for pregnant and breastfeeding women
3
iodine supplementation: public statement
6 Smyth PP (2006) Dietary iodine intakes in pregnancy.
Irish Medical Journal:
99(4); 103.
7 Perez-Lopez FR (2007) Iodine and thyroid hormones
during pregnancy and postpartum.
Gynaecological
Endocrinology:
23(7); 414-428.
8 World Health Organisation Secretariat, Andersson M,
de Benoist B, Delange F and Zupan J (2007)
Prevention and control of iodine deficiency in
pregnant and lactating women and in children less
than 2-years-old: conclusions and recommendations
of the Technical Consultation.
Public Health Nutrition:
10(12A); 1606-1611.
9 Australian Population Health Development Principal
Committee (2007)
The Prevalence and Severity of
Iodine Deficiency in Australia.
Report Commissioned
by the Australian Health Minsters Advisory Committee.
10 Seal JA, Doyle Z, Burgess JR, Taylor R and Cameron AR
(2007) Iodine status of Tasmanians following voluntary
fortification of bread with iodine.
Medical Journal of
Australia:
186 (2); 69-71.
11 Morreale de Escobar G, Jesús Obregón M and Escobar
del Rey F (2007) Iodine deficiency and brain
development in the first half of pregnancy.
Public
Health Nutrition:
10; 1554-1570.
12 Aghini Lombardi FA, Pinchera A, Antonangeli L, Rago
T, Chiovato L, Bargagna S, Bertucelli B, Ferretti G,
Sbrana B, Marcheschi M (1995) Mild iodine deficiency
during fetal/neonatal life and neuropsychological
impairment in Tuscany.
Journal of Endocrinological
Investigation:
18; 57-62.
13 Vermiglio F, Lo Presti VP, Moleti M, Sidoti M, Tortorella
G, Scaffidi G, Castagna MG, Mattina F, Violi MA, CrisÃ
A, Artemisia A, Trimarchi F (2004) Attention deficit and
hyperactivity disorders in the offspring of mothers
exposed to mild-moderate iodine deficiency: a possible
novel iodine deficiency disorder in developed
countries.
Journal of Clinical Endocrinology and
Metabolism:
89; 6054-6060.
NHMRC
14 Choudhury N, Gorman KS (2003) Sub-clinical prenatal
iodine deficiency negatively affects infant development
in Northern China.
Journal of Nutrition:
133; 3162-3165.
15 World Health Organization /United Nations Children’s
Fund /International Council for Control of Iodine
Deficiency Disorders (2007)
Assessment of iodine
deficiency disorders and monitoring their elimination:
a guide for programme managers.
– 3rd ed, WHO.
16 World Health Organization: Regional Office for the
Western Pacific (2005-2009).
Micronutrient deficiencies.
Available online at http://www.wpro.who.int/.
17 Food Standards Australia New Zealand (2008)
Approval
Report Proposal P1003 – Mandatory Iodine Fortification
for Australia.
Commonwealth of Australia. Available
online at http://www.foodstandards.gov.au.
18 Burgess JR, Seal JA, Stilwell GM, Reynolds PJ, Taylor
ER and Parameswaran V (2007) A case for universal
salt iodisation to correct iodine deficiency in
pregnancy: another salutary lesson from Tasmania.
Medical Journal of Australia:
186; 574-576.
19 Li M, Eastman CJ, Waite KV, Ma G, Zacharin MR,
Topliss DJ, Harding PE, Walsh JP, Ward LC, Mortimer
RH, Mackenzie EJ, Byth K and Doyle Z (2008) Are
Australian children iodine deficient? Results of the
Australian National Iodine Nutrition Study.
Medical
Journal of Australia:
188(11); 674.
20 Eastman, C (2009) Personal communication at expert
group meeting, 28 August 2009, NHMRC Canberra.
21 Teas J, Pino S, Critchley A, and Braverman LE (2004)
Variability of Iodine Content in Common Commercially
Available Edible Seaweeds.
Thyroid:
14(10); 836-41.
22 Food Standards Australia New Zealand (2009)
Iodine
Supplements Available in Australia,
unpublished survey
data provided by FSANZ, Canberra.
nHmrC Public Statement: Iodine supplementation for pregnant and breastfeeding women
4

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