Iodine

Question 1

Iodine

Answer 1

• Iodine (I) is a component of thyroid hormones which regulate the metabolic rate of all cells in the body.
• Iodine from food is efficiently absorbed and converted in the GI tract to Iodide ions (close to 100% of dietary iodine is absorbed
• Iodine levels in soil vary widely globally but are relatively low.
• The Ocean is Earth’s main source of iodine.

Question 2

Iodine Food Sources

Answer 2

Sea vegetables (excellent source);
Ocean fish and shellfish such as cod and scallops;
Iodine is also in eggs & dairy foods (due to the fortification of animal feed) with small amounts in plants depending on the soil.

Question 3

Iodine Roles

Answer 3

Thyroid Hormones
Brain Health
Metabolism

Question 4

Iodine: Thyroid Hormones - Functions

Answer 4

• Iodine is an essential component of thyroid hormones . ‘T4’ is named to reflect the presence of 4 iodine atoms, and ‘T3’ 3 iodine atoms.

Question 5

Iodine: Thyroid Hormones - Therapeutic Uses

Answer 5

• Thyroid health (hypothyroidism)

Question 6

Iodine: Brain Health - Functions

Answer 6

• Foetal and infant development: i.e. Brain and Bone formation during pregnancy.

Question 7

Iodine: Brain Health - Therpeutic Uses

Answer 7

Cognitive function during childhood

Question 8

Iodine: Metabolism - Functions

Answer 8

• Critical determinants of energy metabolism in cells.

Question 9

Iodine: Metabolism - Therapeutic Uses

Answer 9

Reversing slow metabolism

Question 10

Making Thyroid Hormones

Answer 10

• The thyroid gland ‘traps’ iodine from the blood.
• Thyroid hormone is made by binding iodine and the amino acid tyrosine to a glycoprotein called thyroglobulin.
• The rate of iodine capture is under the control of TSH (Thyroid Stimulating)
• The selenium dependent enzyme, iodothyronine deiodinase converts the relatively inactive T4 to the active T3.

Question 11

Iodine Deficiency

Answer 11

• In the early 20th century iodine deficiency (ID) was common in the UK / IRE and many other countries around the globe.
• The ‘iodisation’ of table salt began to be implemented in many countries to reverse ID (ID was addressed by the use of iodine fortified cattle feed and an increase in milk consumption).
• ID leads to decline in thyroid hormone production and if prolonged, it can lead to ‘hypothyroidism’ with symptoms like:
fatigue, weight gain and depression. Prolonged ID can lead to a goitre (enlarged thyroid)
• Note: hypothyroidism can occur without ID; e.g. Hashimoto’s Thyroiditis (auto immune).
• Severe ID during pregnancy causes extreme and irreversible mental and physical retardation (a daily intake of 150mcg is recommended by the World Health Organisation).
• Children with even mild iodine deficiency have goitres and perform poorly at school; with treatment mental performance improves.

Question 12

Iodine Toxicity

Answer 12

Acute Iodine Poisoning is rare and only occurs with doses of many grams (the Tolerable Upper Limit (TUL) is 600mcg).

Question 13

Iodine Nutrient Interactions

Answer 13

• Consumption of goitrogenic foods such as soya, millet and raw brassica vegetables may interfere with iodine uptake however, this typically does not have a major clinical effect unless with co-existing Iodine deficiency.
• Hypothyroidism may also be associated with suboptimal Se status Iodine and Selenium deficiencies often overlap.
• Additionally, people with hypothyroidism often have suboptimal levels of Zn, Fe, Cu which can exacerbate iodine deficiency.
• Nutrients such as Tyrosine, Zn, Mg and B vitamins are crucial for iodine utilisation.