iodine - sources and requirements

Last reviewed 06/2021

Iodine (atomic weight 126.9 g per atom) is a micronutrient that is required for the synthesis of the thyroid hormones.

Requirements for Iodine:

*World Heath Organisation requirements

Sources of Iodine (1):

The actual amount of iodine in food varies according to the iodine content of the soil, farming practice, fish species and season. This makes it difficult to estimate iodine per portion. The figures in the table are therefore for guidance only.

**Depending on the season, higher value in winter

Other sources (3) :

• Kelp (per g): 16.8-165 µg
• Vitamins (prenatal, labelled content per daily serving): 75-200 µg
• Amiodarone (per 200 mg): 75,000 µg
• Iodinated contrast (free iodine content, per CT scan): 13,500 µg
• Topical iodine (povidone iodine): variable, usually 1-5%
• Expectorants, mouthwashes, vaginal douches: variable
• Saturated solution of potassium iodide (per drop): 50,000 µg

How much iodine is excess consumption?

• the British Diatetic Association (2) also note that "..As a guide, adult intakes should not exceed 600 mcg/day.." because higher levels may result in thyroid dysfunction
• however it has been stated that "...For adults who are not lactating or pregnant, the US Institute of Medicine, and jointly by the WHO, United Nations Children's Fund (UNICEF) and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD), recommend a daily iodine intake of 150 µg and state a tolerable upper level (the approximate threshold below which notable adverse effects are unlikely to occur in the healthy population) of 1,100 µg per day in adults " (3)

Reference:

• Zimmermann MB. Iodine deficiency. Endocr Rev. 2009;30:376-408
• BDA - Food Fact Sheet; Iodine (accessed 31/8/15)
• Leung AM, Braverman LE. Consequences of excess iodine.Nat Rev Endocrinol. 2014 Mar; 10(3): 136-142.