Chapter 11: Micronutrients in Metabolism

11.9 Iodine

University of Hawai‘i at Mānoa Food Science and Human Nutrition Program

Recall the discovery of iodine and its use as a means of preventing goiter, a gross enlargement of the thyroid gland in the neck. Iodine is essential for the synthesis of thyroid hormone, which regulates basal metabolism, growth, and development. Low iodine levels and consequently hypothyroidism has many signs and symptoms including fatigue, sensitivity to cold, constipation, weight gain, depression, and dry, itchy skin and paleness. The development of goiter may often be the most visible sign of chronic iodine deficiency, but the consequences of low levels of thyroid hormone can be severe during infancy, childhood, and adolescence as it affects all stages of growth and development. Thyroid hormone plays a major role in brain development and growth and fetuses and infants with severe iodine deficiency develop a condition known as cretinism, in which physical and neurological impairment can be severe. The World Health Organization (WHO) estimates iodine deficiency affects over two billion people worldwide and it is the number-one cause of preventable brain damage worldwide.[1]

Figure 11.91 Deaths Due to Iodine Deficiency Worldwide in 2012. Image by Chris55 / CC BY 4.0  

 

Woman with large goiter on neck
Figure 11.92 Iodine Deficiency: Goiter. Credit: A large goiter by Dr. J.S.Bhandari, India / CC BY-SA 3.0

Dietary Reference Intakes for Iodine

Table 11.91 Dietary Reference Intakes for Iodine[2]

Age Group RDA Males and Females mcg/day UL
Infants (0–6 months) 110* Not possible to determine
Infants (7–12 months) 130* Not possible to determine
Children (1–3 years) 90 200
Children (4–8 years) 90 300
Children (9–13 years) 120 600
Adolescents (14–18 years) 150 900
Adults (> 19 years) 150 1,100
Pregnancy 220 Same as non-pregnant
Lactation 290 Same as non-lactating
*denotes Adequate Intake

Dietary Sources of Iodine

The mineral content of foods is greatly affected by the soil from which it grew, and thus geographic location is the primary determinant of the mineral content of foods. For instance, iodine comes mostly from seawater so the greater the distance from the sea the lesser the iodine content in the soil. Because of this high variability in iodine content and the importance of iodine in brain development, many countries add iodine to table salt. Consumption of 1/2 teaspoon of iodized salt meets the RDA for iodine.

Table 11.92 Iodine Content of Various Foods[3]

Food Serving Iodine (mcg) Percent Daily Value
Seaweed 1 g. 16 to 2,984 11 to 1,989
Cod fish 3 oz. 99 66
Yogurt, low fat 8 oz. 75 50
Iodized salt 1.5 g. 71 47
Milk, reduced fat 8 oz. 56 37
Ice cream, chocolate ½ c. 30 20
Egg 1 large 24 16
Tuna, canned 3 oz. 17 11
Prunes, dried 5 prunes 13 9
Banana 1 medium 3 2

 


  1. World Health Organization. “Iodine Status Worldwide.” Accessed October 2, 2011. http://whqlibdoc.who.int/publications/2004/9241592001.pdf.
  2. Dietary Fact Sheet for Health Professionals: Iodine. National Institute of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/. Updated April 28, 2022. Accessed August 2, 2023.
  3. Ibid.
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