DIET

... LPI

Recommended daily intake

Thyroid hormones are continuously broken down and iodine released. Not all of this is re-incorporated by the thyroid into new hormone. The physiological requirement is to compensate (at least) for this loss. It is estimated that adolescents and adults require 50-150 µg/day.
It is empirically clear that about 1 µg/day per kilo of body weight is sufficient to prevent goitre.
To be safe, the recommended daily intake is set at 150 µg/day.

In pregnancy, more iodine is lost through urine. This means that a higher intake is recommended: 200 µg/day.

Breast milk contains about 10mcg of iodine per dl. Nursing mothers should therefore also have a higher intake (200 µg/day).
The recommended intake for children is the same as for adults.

Sources of iodine in the Norwegian diet

Drinking water: large variations, but in the region of 2 µg/l, equivalent to 2-4 µg/person/day.

Fish: 40-90 µg/100 g.

Iodised salt: 5 µg/g.

Milk and milkproducts: since 1950, all fodder has been supplemented with 2 mg iodine/kg, so that a cow gets 5 mg/day. As a result, milk contains from 20-370 µg of iodine/l, and there is a high level of iodine in cheese, butter etc. For example, brunost contains 0,13 mg/100 g.

Table From Dahl L., Johansson L., Julshamn K., Meltzer H.M. (2004) The iodine content of Norwegian foods and diets. Public Health Nutrition 7, 569-576.

Discussion question:
What is the most important message from this table?

Actual intakes of iodine

• Women: ca 135 µg/day

• Men: ca 175 µg/day

If there is an iodine problem in Norway today, it is the risk of over-consumption, if certain iodine-rich foods are consumed (e.g. seaweed).

Discussion question:
What can you conclude from Norwegian levels of intake?

Iodine intake in other countries

• France: 15 µg/g of salt
• USA: iodine added to bread.
• Sweden: 50 µg/g of salt, and milk an important source.
• Finland: 25 µg/g salt, + milk
• Denmark: investigation showed that 4% of old people had visible signs of goitre. From 1998, 8µg/g added to table salt and industrial salt.
• Iceland: intake is 300-350 µg/day, mainly from fish. Iodine is not added to salt.

Excessive intake: -iodine poisoning

Symptoms:

• Overactive gland - hyperthyroidism
• Weight loss
• Trembling
• Nervousness
• Irregular pulse
• Excessive heat production
• Iodine-induced goitre

Iodine intake should not exceed 1 mg/day (for iodine-sensitive individuals, the limit is lower).

Discussion question:
What is the most important message from this table?