| Iodine | ||||||||
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- Why iodine is good for you
- Important iodine facts
- Groups at risk of iodine deficiency
- Symptoms of iodine deficiency
- Iodine and health
- Iodine in foods
- Iodine recommended daily intake (RDI)
- Iodine works best with
- Overdosage, toxicity and cautions for iodine
Iodine is required to make the thyroid hormones that regulate metabolism. While iodine's only function is to make thyroid hormones, it still has a very important role in the body. The thyroid hormones play a big role in growth, cell reproduction, nerve functions and how cells use oxygen. One of the thyroid hormones - thyroxin - regulates how fast energy is used from food. If there is not enough dietary iodine, the thyroid swells up in an effort to make more hormones, a condition that is called hypothyroidism (an underactive thyroid). The swelling is called goitre.
- Iodine deficiency in pregnancy causes a severe form of retardation in the child called cretinism
- Until well into this century, iodine deficiency was a serious problem in the western world. To solve the iodine problem, salt producers began adding iodine to table salt around 1924. Iodine deficient diseases (such as goitre and cretinism) soon disappeared
- Today there are more people developing thyroid cancer and other thyroid disorders and experts believe it is due to the use of sea salt to season food, which has very little iodine in it
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Groups at risk of iodine deficiency
- Pregnant women – pregnant women need to ensure their child has enough iodine to avoid cretinism.
- People with goitre – people with goitre may not have a healthy and proper functioning thyroid. Getting some extra iodine may help the thyroid function properly.
- Eating too many goitrogenic foods – certain foods (such as cabbage, Brussels sprouts, broccoli, turnips, cassava) interfere with the correct functioning of the thyroid. A diet high in these foods may be assisted with iodine supplement or reduction in these foods. Alternatively, cooking goitrogenic foods reduces their gotrogenic effects
People in these groups at risk of deficiency should talk to a medical professional about iodine supplements BEFORE taking them.
Iodine deficiency occurs when less than 50mcg of iodine is taken in each day. Iodine deficiency is normally rare in western countries, but with the high usage of sea salt (which contains little iodine), it is becoming far too common today. Symptoms of iodine deficiency are usually goitre and hypothyroidism. |
- Radiation-induced thyroid cancer - iodine deficient individuals are at increased risk of developing radiation-induced thyroid cancer because they will accumulate greater amounts of radioactive iodine. Potassium iodide administered in pharmaecological doses within 48 hours before or 8 hours after radiation exposure from a nuclear reactor accident can significantly reduce thyroid uptake of and decrease the risk of radiation-induced thyroid cancer. This was noticed in Poland after the Chernobyl nuclear accident
- Fibrocystic breast disease - this is a condition of the breasts that is benign (non-cancerous). One study showed that iodine deficiency leads to fibrocystic breast condition, while iodine supplementation was found to reverse those changes. In another study of women with fibrocystic breast condition were treated with iodine supplementation and 70% reported improvement in their symptoms. Further research needs to be undertaken in order to further validate these findings in larger studies
People who wish to take an iodine supplement should talk to a medical professional BEFORE taking it.
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| FOOD | AMOUNT | iodine (mcg) |
|---|---|---|
| Seaweed, dried | 30g | 100- 18,000 |
| Cod | 85g | 99 |
| Salt (iodized) | 1 gram | 77 |
| Potato with peel, baked | 1 medium | 63 |
| Milk (cow's) | 1 cup | 56 |
| Fish sticks | 2 fish sticks | 35 |
| Navy beans, cooked | ½ cup | 35 |
| Prawns (shrimp) | 85g | 35 |
| Turkey breast, baked | 85g | 34 |
| Egg, boiled | 1 large | 29 |
| Tuna, canned in oil | 85g | 17 |
Iodine recommended daily intake (RDI)
| RDA | lifestage | age | amount |
|---|---|---|---|
| INFANTS | 0-6mths 7-12mths |
110mcg (0.11mg) 130mcg (0.13mg) |
|
| CHILDREN | 1-8yrs | 90mcg (0.09mg) | |
| CHILDREN | 9-13yrs 14-18yrs |
120mcg (0.12mg) 150mcg (0.15mg) |
|
| ADULTS | 19-50yrs | 150mcg (0.15mg) | |
| SENIORS | 51+yrs |
150mcg (0.15mg) | |
| PREGNANT | all ages | 220mcg (0.22mg) | |
| LACTATING | all ages | 290mcg (0.29mg) | |
| TOLERABLE UPPER LIMIT | lifestage | age | AMOUNT |
| INFANTS | 0-12mths | n/a* | |
| CHILDREN | 1-3yrs 4-8yrs |
200mcg (0.2mg) 300mcg (0.3mg) |
|
| CHILDREN | 9-13yrs 14-18yrs |
600mcg (0.6mg) 900mcg (0.9mg) |
|
| ADULTS | 19-50yrs | 1100mcg (1.1mg) | |
| SENIORS | 51+yrs |
1100mcg (1.1mg) | |
| PREGNANT | <18yrs 19-50yrs |
900mcg (0.9mg) 1100mcg (1.1mg) |
|
| LACTATING | <18yrs 19-50yrs |
900mcg (0.9mg) 1100mcg (1.1mg) |
|
| Toxic Levels | >1,500mcg | ||
The tolerable upper limits should only be taken for short periods and only under medical supervision.
* The tolerable upper limit for iodine for infants aged 0-12 months has not yet been determined due to a lack of data about the adverse effects in this age group. The only source of iodine intake should be from food (breast milk and/or baby formula).
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Overdosage, toxicity and cautions for iodine
Acute toxicity (>2000mcg) – swollen heart, stomach irritation, hypersensitivity, blood sickness
Chronic toxicity – brassy taste in the mouth, burning sensation of mouth and throat, decreased thyroid activity, diarrhoea, stomach irritation, goitre, Grave's disease, head cold symptoms, hyperthyroidism, increase salivation. Ironically, goitre can also develop if consistently large amounts of iodine are taken over a long period.
CAUTIONS
People taking lithium carbonate for manic depressive illness should NOT take iodine as it suppresses the thyroid gland and can produce abnormally low thyroid activity.
Be careful when taking extra iodine supplements as excessive amounts can cause hyperthyroidism, a condition where the thyroid overreacts and this can cause another set of problems.
references
- USDA National Nutrient Database - provides nutrient values for foods (accessed 5 January 2005)
- Osiecki, H. The Nutrient Bible. Bio-Concepts Publishing QLD, 2002
- Whitney EN, Cataldo DB, Rolfes SR. Understanding Normal and Clinical Nutrition, 6th Edition. Wadsworth/Thomson Learning, 2002
