Iodine Policy in the United States

Elizabeth N. Pearce, M.D., M.Sc.

Overview

• Dietary iodine requirements and assessment of iodine sufficiency

• Current U.S. iodine nutrition status • Sources of U.S. Dietary Iodine• Iodine recommendations

Recommended Daily Dietary Iodine Intakes

- U.S. Institute of Medicine 2006- WHO, UNICEF, ICCIDD 2007

U.S. Institute of Medicine WHO, UNICEF, ICCIDD

µg/day µg/day0-6 months (AI) 110 0-5 years 90

7-12 months (AI) 130

1-8 years 90

9-13 years 120 6-12 years 120

>13 years 150 >12 years 150

Pregnancy 220 Pregnancy 250

Lactation 290 Lactation 250

Increased demand for thyroid hormone (↑ 50%),requires an additional 50-100 μg iodine:- Thyrotropic regulation by hCG- Estrogen-mediated TBG increase

Placental Type 3 deiodinase

Iodide transferred to the fetus(50-75 μg/day)

Increased renal iodine clearance(↑ 30-50%)

Increased Maternal Dietary Iodine Requirementsin Pregnancy

Increased Dietary Iodine Requirementsin Lactation

• Normal lactating breast ducts concentrate iodide (via sodium iodide symporter), secreting it into milk

• Only source of iodine nutrition for breastfed infants

Tazebay et al Nat Med 2000; 6:859-60

Tolerable Upper Limits for Iodine Exposure

U.S. Institute of Medicine

WHO, UNICEF, ICCIDD

µg/day µg/day

0-12 months unknown Infants 180

1-3 years 200 Pregnancy 500

4-8 years 300 Lactation 500

9-13 years 600

14-18 years 900

19-50 years 1,100

- U.S. Institute of Medicine 2006- WHO, UNICEF, ICCIDD 2007

WHO/ICCIDD/UNICEF, 2007

Median Urinary Iodine Concentration (μg/L)

Corresponding Iodine Intake (μg/day)

Iodine Nutrition

<20 <30Severe

deficiency

20-49 30-74Moderate deficiency

50-99 75-149 Mild deficiency

100-199 150-299 Optimal

200-299 300-449More than adequate

>299 >449 Possible excess

Population Urinary Iodine Values and Iodine Nutrition

For children < age 2, Urinary iodine ≥100 μg/L = sufficiency

Urinary Iodine Values and IodineNutrition in Pregnancy and Lactation

WHO Public Health Nutr 2007

Population groupMedian Urinary Iodine Concentration (μg/L)

Optimal Excessive

Non-pregnant adults

100-199 >299

Pregnant Women 150-249 ≥500

Lactating Women ≥100

Overview

• Dietary iodine requirements and assessment of iodine sufficiency

• Current U.S. iodine nutrition status • Sources of U.S. Dietary Iodine• Iodine recommendations

U.S. Goiter Belt (pre-1920s)– 26 - 70% of children had goiter

Morton Salt, 1920s

168 160 164144145

320

0

50

100

150

200

250

300

350

400

1971-74

1988-94

2001-02

2003-04

2007-08

2009-10

Total

Males

Females

Median U.S. Urinary Iodine ConcentrationNHANES 1971-2004

Hollowell et al. JCEM 1998; 83:3401-8; Caldwell et al. Thyroid 2005;15:692-9; Caldwell et al. Thyroid 2008;18:1207-14; Caldwell et al. Thyroid 2011;21:419-27; Caldwell et al, Thyroid 2013; 23:927-37

Me

dia

n U

rine

Iod

ine

Co

nce

ntra

tion

(μg

/L)

% of U.S. Population with Urinary Iodine<50μg/L: NHANES I and NHANES III

JG Hollowell et al. J Clin Endocrinol Metab1998; 83:3401-8

Age (years)

Median urinary iodine concentration (UIC) among pregnant women, NHANES

Med

ian

UIC

μg

/L

wit

h 9

5%

CI

NHANES Survey

Insufficient iodine intake

Adequate iodine intake

Above requirement iodine intake

Hollowell et al, JCEM 1998; 83:3401-8; Caldwell et al. Thyroid 2005;15:692-9; Caldwell et al. Thyroid 2008;18:1207-14; Caldwell et al. Thyroid 2011;21:419-27; Caldwell et al. Thyroid 2013;23:927-37

Median UIC in pregnancy 129 µg/L2005-2010

0

100

200

300

400

500

1 2 3 4 5

Me

dia

n U

rin

ary

Iod

ine

(g

/L)

Urinary Iodine by Quintiles

150 g/L~220 g/daydietary intake(RDA for pregnancy)

Urine Iodine in a Sample of100 Pregnant Women Living in Boston

5296

149

230

438

EN Pearce et al. Thyroid 2004; 14:327-8

Iodine Status of Lactating Boston-Area Women and their Infants

AM Leung et al. Thyroid 2012;22:938-43.

Iodine Concentration in µg/Lmedian (interquartile range)

Breast Milk 45.6 (4.3-1080)

Maternal Urine 101.9 (27-570)

Infant Urine 197.5 (40-785)

64 mother-infant pairsInfants age 1-3 months

Pearce EN et al. J Clin Endocrinol Metab 2007;92:1673-7

US Infant Formulae Iodine Content

U.S.: allowable 5-75 µg/100 kcal

JH Gordon et al. Thyroid 2014;1309-13

Urinary Iodine Concentrations in Breastand Bottle-Fed Infants from the Boston Area

n=44 n=39 n=10

NHANES Survey

Insufficient iodine intake

Adequate iodine intake

Above requirementiodine intake

Excessive iodine intake

Median urinary iodine concentration amongchildren age 6-11, NHANES

Med

ian

UIC

μg/

L w

ith 9

5% C

I

Hollowell et al, JCEM 1998; 83:3401-8; Caldwell et al. Thyroid 2005;15:692-9; Caldwell et al. Thyroid 2008;18:1207-14; Caldwell et al. Thyroid 2011;21:419-27; Caldwell et al. Thyroid 2013;23:927-37

Overview

• Dietary iodine requirements and assessment of iodine sufficiency

• Current U.S. iodine nutrition status • Sources of U.S. Dietary Iodine• Iodine recommendations

0102030405060

Dairy

Mea

t, Fis

h, Poul

tryG

rain

Fruit,

Veg

Fats,

Oils

Sugars

Bever

ages

Egg

Median Iodine Content of Adult* Diets2003-2004 FDA Total Diet Study

% D

aily

iodi

ne I

ntak

e

CW Murray et al. J Expo Sci Environmen Epidemiol 2008;18:571-80.

*Women age 25-30

Salt in the U.S. Diet

77% Restaurant and processed foods

12% Naturally occurring

6% Whileeating

5% While cooking

• ~77% of salt in U.S diet from restaurant/processed food, usually not iodized

•~11% table salt added at the table or in cooking, 53% of table salt in U.S. is iodized at 60-100 ppm

• ~50% of reproductive agewomen never/rarely use table salt

Mattes & Donnelly. J Am Coll Nutr 1991;10(4):383-93.Maalouf J et al. Nutrients 2015;1691-5

Bread Iodine Content

• Iodate dough conditioners used starting 1940s. Use 1970s-1990s.

• Boston-area supermarkets 2001-2002:– 20 brands measured– 3 breads >313 μg I/slice– Others 2.2-54 μg I/slice (mean 10 μg/slice)

• Package labels inaccurate

EN Pearce et al. J Clin Endocrinol Metab 2004; 89:3421-4

Mean Iodine Content of New EnglandCows’ Milk by Season

μg

I pe

r 25

0 m

l (~

1 cu

p)

n = 18 brandsp <0.0005

Winter Summer

116

91

EN Pearce et al. J Clin Endocrinol Metab 2004; 89:3421-4

Iodine Sources in U.S. Cows’ Milk

• Cattle feed– Cows’ milk iodine content increased 300-500%

1965-1980 due to increased I in cattle feed– Organic iodine ethylenediamine dihydroiodine

(EDDI) content of cattle feed limited 1986 to 10mg/cow/day

• Iodophor disinfectant in teat dip/udder wash– Up to 1% available iodine

EN Pearce et al. J Clin Endocrinol Metab 2004; 89:3421-4

Median Urinary Iodine Levels in U.S. Vegetarians and Vegans

78.5

147

0

50

100

150

200

vegans vegetarians

AM Leung et al. J Clin Endocrinol Metab 2011;96:E1303-7.

Optimal iodine intake (WHO)

(µg/L)

Median U.S.

urinary iodine

164

n=62 n=78

Overview

• Dietary iodine requirements and assessment of iodine sufficiency

• Current U.S. iodine nutrition status • Sources of U.S. Dietary Iodine• Iodine recommendations

U.S. Guidelines

Women who are planning to be pregnant or are pregnant or breastfeeding shouldsupplement their diet with a daily oral supplement that contains 150 µg of iodine.

• A Stagnaro-Green et al. Thyroid 2011;21:1081-125• L De Groot L et al. J Clin Endocrinol Metab 2012;97:2543-65• SG Obican et al. Birth Defects Res A Clin Mol Teratol 2012;94: 677-682• AAP Council on Environmental Health. Pediatrics 2014;133:1163-6

CO Gregory et al. Thyroid 2009;19:1019-20

Percentage of Reproductive Age U.S. WomenReporting Supplement Use Within 30 Days

43.4

76.967.8

20.2 20.314.5

0102030405060708090

Any Supplement

Supplementwith Iodine

Pregnantn=4322 n=983 n=143

Based on NHANES 2001-2006

%

Prescription prenatal multivitamins

(n = 96)

28% (n=27) contain iodine

Non-prescription prenatal multivitamins

(n = 127)

69% (n=87) contain iodine

Proportion of U.S. Prenatal Multivitamins

Containing Iodine

AM Leung et al. N Engl J Med 2009;360:939-40

January 27, 2015—Dietary supplement manufacturers should include a daily serving of at least 150 mcg of iodine in all multivitamin/mineral supplements intended for pregnant and lactating women in the U.S., the Council for Responsible Nutrition (CRN) advises in guidelines for industry released today.

CRN recommends that dietary supplement companies comply within twelve months.

Conclusions• Overall dietary iodine intake is currently

sufficient in the U.S.• However, there are concerns about mild

iodine deficiency among women during pregnancy and lactation– Recommend iodine-containing prenatal

multivitamin

• Further monitoring is needed