Presentation by: Omar Dary

Place:World Nutrition – 2012Rio de Janeiro, Brazil

29-April-2012

Monitoring Salt and Iodine Intakes is a Critical Issue to Adjust Salt

Fortification Programs

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Content

1. The Dietary Reference Intakes (DRI) of iodine

2. The misinterpretation of the 100 µg/L cut-off point for urinary iodine to assess appropriate iodine intake

3. Advantage of estimating the 24-h iodine excretion

4. Estimating efficacious and safe iodine intakes for the whole population

5. Transforming those intakes in iodine contents in salt

6. Conclusions

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Iodine Dietary Reference Intakes (µg/day)

Figure modified from Institute of Medicine, the Academies of Science, USA.

86 120 450 Iodine: µg/d

1500 mg/d Na salt: 3.7 g/dValues are for children 6-9 years old

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Median Urinary Iodine Concentration in 6-12 y old children in Germany

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 20080

20

40

60

80

100

120

Med

ian

UIC

(µg/

L)

Mandatory labeling

Decline in the use of iodized

salt by the food industry: 35 to

29%

Source: Johner et al. Br J Nutr 2011.

Authorizing food industry to use iodized salt

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Iodine and sodium intakes in 6-12 y old children in Germany (Medians)Parameter 2004-2006 2007-2009UIC (µg/L) 110 98UIE (µg/d) 86 84Iodine Intake (µg/d) * 101 99% < EAR 17 % 16 %

Source: Johner et al. Br J Nutr 2011.

* Assuming that 85% of iodine and 90% sodium intakes are excreted in urine

Parameter 2004-2006 2007-2009U-Na-Excretion (g/L) 1.91 1.99U-NaCl-Excretion (g/d) 4.8 5.0Salt Intake (g/d) * 5.3 5.6

References: EAR iodine = 86-107 µg/d; UL salt = 3.7-4.6 g/d

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Sources: USA-NHANES; UIC – 2007-2008, except non-pregnant and pregnant women 2005-2008, Caldwell et al. Thyroid 2011; 21: 419; body weight 2003-2006, McDowell et al., Anthropometric reference data for children and adults; National Health Statistics Report 2008; 10.

UIE (ug I/d) estimated by multiplying the reported UIC (ug I/L) for the calculated urinary volume of each age- and gender group, based on body weight:

Urinary volume (L/d) = 0.009 L/h.kg x 24 h/d x wt (kg) – from IOM/ Academies of Sciences of the USA: Dietary Reference Intakes for iodine and other nutrients. National Academy Press. 2001.

0

50

100

150

200

250

300

350

400

UIC(ug I/L)UIE(ug I/d)

UIC and estimated UIE in the USA

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Ensuring iodine efficacy for everyone: “adjusted” EAR

Variable Ch 9-13 M 19-30 F 19-30 Pregnant Women

Lactating women

EAR (µg I/d) 73 95 95 160 209

Energy (kcal/d) 2069 3050 2400 2637 2804

µg I /100 kcal 3.5 3.1 4.0 6.1 7.5

Conclusions: The groups at the highest risk of iodine inadequacy are the pregnant and lactating women. For protecting the whole population the adult females should have an iodine intake 1.87 times higher than their corresponding EAR value of iodine: 95 x 1.87 = 178 180 µg/d.

Reference to F 19-30 years old 0.88 0.85 1.00 1.52 1.87

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Ensuring iodine safety for everyone: “adjusted” UL

Variable Ch 1-3 Ch 9-13 M 19-30 F 19-30 Pregnant women

UL (µg I/d) 200 600 1100 1100 1100

Energy (kcal/d) 1062 2069 3050 2400 2637

µg I/ 100 kcal 19 29 36 46 42Reference to F 19-30 years old 0.41 0.63 0.78 1.00 0.91

Conclusion: The groups at the highest risk of receiving excessive amounts of iodine are the children 1-3 years old.For protecting the whole population the adult females should have an iodine intake 0.41 times lower than their corresponding UL value of iodine: 1,100 x 0.41 = 451 500 µg/d.

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Potential of “fortifiable” salt (hypothetical)

Salt sources China Japan USADiet 10 % 30 % 50 %

Processed foods 12 % 60 % 35 %Discretionary salt (cooking + table) 78 % 10 % 15 %Proportion of fortifiable salt 90 % 70 % 50 %

Conclusion: Both discretionary salt and processed foods should be iodized; depending only on discretionary salt would be insufficient for developed countries and countries in epidemiological and economic transition.

Based on data from Elliot and Brown, “Salt intakes around the world”. WHO, 2007. Diet salt is assumed from fish, meat, poultry, milk, cheese, ham, margarine and tomatoes.

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Estimating efficacious and safe iodine contents in “fortifiable” salt

CountrySalt intake (g/d)* “Fortifiable” salt

(g/d)**Average iodine

content (mg I/kg) ***P-10 P-90 P-10 P-90 Efficacious Safe

PRC-South 3.5 10.9 3.1 9.8 58 51

USA¶ 4.6 10.9 2.3 5.5 78 92

Japan 6.3 14.4 4.4 10.1 41 50

PRC-North 8.6 19.0 7.8 17.1 23 29

* Using the adult females as the reference groups, and as the “average” population group. Data from Elliot and Brown, “Salt intakes around the world”. WHO, 2007. ** Proportions of “fortifiable” salt in prior table. *** Efficacious: “adjusted” EAR at P-10; Safe: “adjusted” UL at P-90. And, assuming that the only source of iodine is the salt.¶ If one assumes that USA received 50% iodine through the diet (milk mainly), then the iodine content in salt could be reduce by half; i.e. around 40 mg I/kg.

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Conclusions

1. UIC (µg/L) is an unreliable indicator to estimate iodine intake; it is preferable using UIE (µg/d)

2. Intake of iodine from salt and sodium are directly correlated with the energy intake of each person

3. Estimation of daily excretion of both iodine and sodium (NaCl) is needed to design efficacious and safe iodization programs

4. Both processed foods and discretional salt should be iodized in a content that is proportional to the sodium intake from these sources in each population