1. Thyroid hormone production: Iodine is a crucial component of thyroid hormones, which regulate metabolism, growth, and development.
2. Brain development: Iodine plays a critical role in the development of the fetal brain and nervous system. Severe iodine deficiency during pregnancy can lead to cognitive impairments, including intellectual disability.
3. Immune system function: Iodine plays a role in supporting immune system function and helping the body defend against infections.
4. Breast tissue health: Iodine is also important for the health of breast tissue, particularly in women.

1. Seafood: Fish and shellfish are particularly rich in iodine. Seaweed, which is also high in iodine, is a common food in many Asian countries.
2. Dairy products: Milk, cheese, and yogurt can be good sources of iodine, particularly if the animals were fed iodine-fortified feed.
3. Eggs: Eggs are a good source of iodine, particularly if the hens were fed iodine-fortified feed.
4. Iodized salt: Table salt that has been fortified with iodine is a common source of iodine in many countries.

Iodine deficiency is caused by insufficient intake of iodine in the diet. This can occur in areas where the soil is poor in iodine, and thus crops grown in that soil will also be low in iodine. In addition, people who don’t consume enough iodine-rich foods or don’t use iodized salt may also develop iodine deficiency.

The symptoms of iodine deficiency depend on the severity of the deficiency and can range from mild to severe. Mild iodine deficiency may not cause any noticeable symptoms, but moderate to severe iodine deficiency can lead to a range of health problems, including:

1. Goiter (enlarged thyroid gland) – This occurs when the thyroid gland is unable to produce enough thyroid hormone due to a lack of iodine, leading to the production of more thyroid-stimulating hormone (TSH) and enlargement of the thyroid gland.
2. Hypothyroidism – This is a condition in which the thyroid gland does not produce enough thyroid hormone, leading to fatigue, weight gain, cold intolerance, and other symptoms.
3. Intellectual disabilities and developmental delays – Iodine is essential for the development of the brain, and severe iodine deficiency during pregnancy and infancy can result in permanent brain damage.
4. Miscarriage and stillbirth – Iodine deficiency during pregnancy increases the risk of miscarriage, stillbirth, and other pregnancy complications.
5. Cretinism – This is a severe form of intellectual disability and physical stunting that occurs when a baby is born to a mother who has severe iodine deficiency during pregnancy.
6. Increased risk of thyroid cancer – Severe and prolonged iodine deficiency can increase the risk of thyroid cancer.