Iodine deficiency is on the rise in New Zealand, and those eating a paleo diet may be affected.
Here is a map of Global Iodine deficiency (Source http://www.iccidd.org/)
New Zealand soils contain low amounts of iron, iodine and selenium (I’ll talk about selenium deficiency in NZ in another post) Goitre (swollen thyroid due to iodine deficiency) was endemic in New Zealand in the late 1800s to early 1900s. Iodised table salt introduced in 1924 ensured goitre virtually disappeared by 1950. Currently though iodised salt has gone out of vogue, and is sea salt is popular. In addition non iodised salt is now used in food manufacture.
This graph shows iodine consumption has reduced dramatically in New Zealand over the last 30 years (NZ Total Dietary Survey) We now have epidemic levels of mild iodine deficiency in New Zealand. It is possible that paleo and other health conscious people are more at risk.
Where does the iodine in your diet come from if not from soil?
Seafood; fish shellfish and seaweed, iodised salt, milk and eggs are the main sources. Meat and cereal also contain some iodine.
Iodine in milk results from the use of iodophors (iodine based cleaning products) used for sanitising milk machines. In the 1980s however iodophors started being replaced by alternative cleaners, and iodine from milk decreased.
Iodised salt is still available at the supermarket, however it has gone out of vogue in the health conscious, and has been replaced by non iodised sea salt. In addition non iodised salt is now used in food manufacture, and health conscious don’t add much salt to food.
Iodine in vegetables reflects the soil they are grown in. Boiling vegetables in water causes iodine to leach out.
What happens if you don’t consume enough iodine?
Iodine deficiency may lead to goitre, hypothyroidism, and impaired mental and physical development. Dietary iodine requirements increase from childhood to adulthood, with the greatest requirement being for lactating and pregnant women. Insufficient iodine in pregnancy will affect development of the baby, both reduced IQ (12 – 18 points) and ADHD are more prevalent in babies born to iodine deficient mothers. (Attention deficit and hyperactivity disorders in the offspring of mothers exposed to mild-moderate iodine deficiency: a possible novel iodine deficiency disorder in developed countries)
How do you measure iodine deficiency?
Urinary Iodine Concentration, either a 24 hour urine, or a spot test.
This test reflects iodine intake the previous few days. A 24 hour urine is preferable. Spot tests are not suitable for individuals and are used for population studies.
Greater than 90% of ingested iodine is excreted in the urine, so this test will reflect only recent iodine intake.
Iodine loading test
This is available through alternative health practicioners. A specified oral dose of iodine/iodide is given and urine is collected for the subsequent twenty-four hours. The test is based on the concept that the body has specific and saturable mechanisms to take up iodine/iodide. When maximal retention is attained, the percentage of an iodine/iodide load that is retained decreases and the percentage urinary excretion increases. The load test requires a complete twenty-four hour urine collection. http://www.fxmed.co.nz/urine-iodine-pre-and-post-loading/
Thyroid Stimulating Hormone (TSH)
TSH reflects the levels of circulating thyroid hormone. If thyroid hormones are low in the bloodstream more TSH is sent from the brain to ‘tell’ the thyroid to work harder. So a high TSH means there are low thyroid hormones (T4).
However this test is not very sensitive for iodine deficiency in children and adults. It is however very sensitive for iodine status in newborns. Testing a newborn for TSH is really useful in picking up hypothyroidism caused by iodine deficiency. Given the brain is developing rapidly, picking up a deficiency could save a child from developmental delay.
TSH can also be high if the thyroid is damaged due to auto-immune thyroid disease (Hashimoto’s)
Thyroglobulin (Tg) is a protein made only in the thyroid. If dietary iodine is deficient Tg levels rise, the amount of Tg in the bloodstream is correlated to iodine deficiency.
If you have auto-immune thyroid disease (Hashimoto’s) you actually make antibodies against this protein. Testing for Tg antibodies is important to do at the same time.
Thyroid hormone concentrations
Although thyroid hormones are affected by insufficient iodine, T4 and T3 can still measure in the normal range despite a low iodine intake
You may be iodine deficient in New Zealand if:
- You don’t use iodised salt
- You don’t eat bread (using iodised salt in bread has been mandatory in NZ since 2009)
- You consume little seafood; shellfish, fish, seaweed.
- You don’t drink milk
If you live in New Zealand it is critical you consume enough iodine. Top food sources include:
- Seafood and seaweed (such as kelp and nori), is especially high in iodine
- Use iodised salt. This is not the same as sea salt. You need to check it is the correct one as sea salt is an insufficient source of iodine
- Take an iodine supplement – or a multivitamin with 50 – 150 ug of iodine per day. If you are pregnant you need 100 – 200 ug of iodine a day. Many New Zealand pregnancy vitamins now contain iodine. (Check the label)
Don’t take too much iodine.
If you have auto-immune thyroid disease (Hashimoto’s), adding a lot of iodine can cause the thyroid to swell and the disease to be exacerbated. You may have Hashimoto’s and be unaware of it. It is critical to take selenium as well as iodine – selenium is also deficient in New Zealand soils and is critical for making anti-oxidants that protect the thyroid. As well it is required to convert the thyroid hormone T4 into T3.