What is Iodine?
Iodine is a nonmetal that is typically found and functions in the form of Iodide. The human body contains about 15–20 mg of iodide, where 70 - 80 % is found in the thyroid gland. The mineral used in antiseptics such as povidone-iodine which is used against yeast, fungi, bacteria, viruses, spores, and protozoa.
Why is it important?
Aside from its medical uses for wounds and surgery, dietary iodide is used by the body to synthesize thyroid hormone which is needed for growth and development and for regulating metabolism. The Recommended Dietary Allowance for Iodide is 150 micrograms per day for adults. However, the requirement is higher during pregnancy at 220 micrograms per day, followed by an increase to 290 micrograms per day during lactation to meet the increased metabolic demands during pregnancy and lactation. Iodide is also important for growing children for normal growth and development. Iodide deficiency may cause hypothyroidism or goiter which can result in poor growth, poor organ maturation, delayed sexual maturity, and mental deficits which may negatively affect school performance and future productivity.
Hypothyroidism during pregnancy may lead to infants with cretinism - a condition of stunted growth and mental retardation. These individuals exhibit large heads relative to the body, are deaf, and have coarse features. This condition is permanent once the child is born thus adequate iodine intake during pregnancy is key to preventing this condition.
Other possible consequences of iodine deficiency during pregnancy include Pre-eclampsia, low-birth-weight infants, miscarriages, and stillbirths.
How can Iodine deficiency be prevented and what are the food sources of Iodine?
Prevention and treatment of goiter usually begin with iodide-rich foods, including iodized salt, which will shrink the
goiter with time but will not necessarily correct any of the developmental problems (growth and mental aptitude) in children. Thus, adequate iodine intake early in pregnancy and in childhood is important to prevent irreversible consequences.
Marine seafood (shrimp, oysters, ocean fish, mollusks) is typically a better source of iodide than freshwater
fish. Dairy foods may be a fair source of iodide. Again, the iodide content of cow’s milk reflects the iodide content of the cow’s feed or the soil of its grazing region. Iodized salt is also a good source where it contains one part sodium iodide for every 1,000 parts of salt. The following are nutritional tips on how to prevent or treat iodine deficiency:
1. Eat Iodine-rich foods.
Iodine is a component of thyroid hormone. The following are Iodine rich food sources:
- Iodized salt or Processed Foods with Iodized salt
- Fish and seafood
- Seaweeds
- Egg
2. Use iodized salt or supplements with Iodine in moderation.
Excessive iodine from the diet or from supplements may worsen hypothyroidism due to the Wolff-Chaikoff effect where there is a temporary reduced thyroid hormone synthesis due to high levels of Iodine. When the Iodine levels go back to normal range, thyroid hormone synthesis will resume. Based on the Philippine Dietary Reference Intakes (2015), the recommended Iodine intake per day for adult Filipino Males and Females 19-29 years old is 150 ug which is equivalent to ¾ to 1 teaspoon of iodized salt (National Institutes of Health, 2021).
3. Lessen or avoid goitrogenic foods.
Vegetables from the Brassica genus contain goitrogens or substances that may hinder thyroid hormone synthesis. Lessen or avoid the following goitrogens:
- Cabbage
- Cauliflower
- Broccoli
- Radish
- Turnips
- Cassava
Who needs to watch their Iodine intake?
Individuals who need to restrict dietary iodide intakes are those with hyperthyroidism or those being treated with thyroid cancer. They must limit dietary iodide intake to less than about 50 mg of iodide/day. Most commonly restricted foods include all seafood, iodized salt, eggs and dairy products, and soybean/soybean products such as tofu, soy milk, and soy sauce.
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References
Food and Nutrition Research Institute, Department of Science and Technology (2018). Philippine Dietary Reference Intakes 2015.
Gropper, S.S., Smith, J.L., Carr, T.P. (2021). Advanced nutrition and human metabolism, 8th ed. Cengage Learning.
Medeiros, D.M. & Wildman, R.E.C. (2019). Advanced Human Nutrition, 4th ed. United States of America: Jones & Bartlett Learning.
National Institutes of Health (2021). Iodine: Fact Sheet for Health Professionals. National Institutes of Health. Retrieved from https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/.
Sharma R, Bharti S, Kumar KH. Diet and thyroid - myths and facts. (2014). J Med Nutr Nutraceut. Retrieved from: https://www.jmnn.org/text.asp?2014/3/2/60/131954
