Iodine is required for the development of essential thyroid hormones. Iodine is a trace element in certain foods that is naturally present, added to others, and available as a dietary supplement. Thyroid hormones play a significant role in a wide range of body functions including metabolism, bone health, immune response, and central nervous system (CNS) growth.

Iodine is an important part of the thyroid hormones Thyroxine (T4) and T3. Thyroid hormones control other essential biochemical processes, including protein synthesis and enzymatic activity, as well as being vital determinants of metabolism.

Not enough dietary iodine can cause severe problems in adults including stunted development in young children and an enlarged thyroid gland (goiter). Within the thyroid gland in the neck, about 70 to 80 percent of iodine is contained. The rest lies in the hair, skin, ovaries, and other body parts.


Daily Required Intake of Iron

You require just a relatively limited quantity of iodine (about one teaspoonful for most adults over a lifetime) relative to certain nutrients, which is why the required doses are expressed in micrograms (mcg, or μg). The prescribed dietary iodine intake depends on your age and stage of your life.

According to National Institutes of Health the Recommended Dietary Allowance (RDA) for iodine:

Birth to 6 months110 mcg*110 mcg*
7–12 months130 mcg*130 mcg*
1–3 years90 mcg90 mcg
4–8 years90 mcg90 mcg
9–13 years120 mcg120 mcg
14–18 years150 mcg150 mcg220 mcg290 mcg
19+ years150 mcg150 mcg220 mcg290 mcg

* Adequate Intake (AI)


Sources of Iodine


For most adults, the minimum daily dose of iodine (RDA) is 150 mcg a day. Such standards are higher for women who are pregnant or breastfeeding.
In addition, one-third of the population is at risk of deficiencies, particularly those living in areas with only a small amount of iodine in the soil, including in European countries.

Here are the best sources of iodine:

  • Seaweed – Seaweed is a healthy source of vitamins, minerals, and antioxidants. It is low in calories too. Three common varieties of seaweed include kombu kelp, wakame, and nori. 1 gram (g) of whole comprises 16 to 2984 mcg of iodine.
  • Baked COD – Cod is a popular white fish that has a moderate taste and is soft in texture. This is relatively low in fat and calories but has a wide variety of minerals and nutrients including iodine. A piece weighing 3 ounces (85 grams) contains 99 mcg or 65 percent of RDA.
  • Dairy products – Significant sources of iodine are dairy products. 1 cup of low-fat milk contains 56 mcg of RDA or 37%. Yogurt is a healthy source of iodine in dairy too. One cup of plain yogurt contains nearly half of the RDA.
  • Iodized Salt – Around 71 mcg of iodine is found in 1/4 teaspoon of iodized salt, which is 47 percent of the RDA. Yet salt contains sodium, too.
  • Tuna – Tuna is a fairly strong source of iodine since it contains 17 mcg or three ounces or about 11 percent of RDA. Tuna is also a healthy source of omega-3 fatty acids which can reduce heart disease risk.
  • Egg – The bulk of iodine is found in the yolk of eggs. One big egg contains 24 mcg or 16 percent of the RDA on average. Just one entire egg contains a lean protein supply, healthy fats, and a wide variety of vitamins and minerals.
  • Shrimp – Shrimp is a healthy protein source, with other minerals, including iodine. Three ounces of shrimp provide 35 mcg of iodine, around 23 percent of RDA.


Health Benefits of Iodine

Iodine is a critical component of thyroid hormones, the main and well-understood feature of the mineral. Your thyroid gland produces the thyroid hormones thyroxine (T4) and triiodothyronine (T3), all iodide (a type of iodine) in it.

Iodine is swallowed by chewing and is ingested rapidly in the stomach and small intestine. It passes through the bloodstream, and iodine receptors (located in the thyroid) bind to it and take it in from here.

T4, which contains four iodide molecules, is an inactive precursor to the active thyroid hormone T3 which contains three iodide molecules. This means that after T4 is developed by the thyroid gland and released into the bloodstream, it is then converted to T3 which interacts with most body cells.


Iodine Deficiency


Iodine deficiency has many negative effects on growth and development and is the world’s most severe form of intellectual disability preventable.

Groups at risk of iodine deficiency:

  • People living in areas where the soils are iodine deficient. Mountainous areas such as the Himalayas, the Alps, and the Andes and flood-prone river valleys, especially in South and Southeast Asia, are among the world’s most iodine-deficient regions.
  • People that consume foods containing goitrogens with negligible iodine status.
  • People who do not use salt which is iodized.
  • Pregnant women.

The signs are somewhat similar to those of weak thyroid hormones, or hypothyroidism. Since iodine is used to produce thyroid hormones, a shortage of iodine means that the body can not produce enough of them, leading to hypothyroidism.

Here are some sign and symptoms of iodine deficiency:

  • Unexpected weight gain
  • Neck swelling
  • Hair loss
  • Fatigue
  • Dry skin
  • Changing Herat Beat
  • Feeling colder than usual
  • Irregular periods
  • Constipation

Iodine deficiency can cause serious problems for fetuses, babies, and young children to develop. If you are pregnant or breastfeeding, and you are deficient in iodine, your baby is, particularly at danger.


Overdose of Iodine

In fact, mild absorption of iodine by the ingestion of iodized salt or by the food in the diet would not be troublesome as extra iodine is quickly eliminated by the urine.

The recommended maximum intake of iodine is 1,100 mcg per day for all adults, and 200 to 300 mcg per day for children under the age of 8.

Iodine affects the thyroid in a nuanced way. Too much and too little iodine will lead to goiter problems as well as other thyroid problems. For that cause, before taking iodine supplements, it is essential to talk with a doctor.

The iodine poisoning can cause:

  • Fever
  • Burning of mouth and stomach
  • Weak pulse
  • Abdominal pain
  • Nausea
  • Vomiting

Too much iodine can contribute to papillary cancer of the thyroiditis and the thyroid.