Many of us know iodine only as that pungent brown antiseptic liquid the school nurse used to dab over our grazed knees or as an element on the periodic table. But did you know that iodine is also a vital nutrient that becomes even more important during pregnancy and early infancy? Read on to know more about this forgotten mineral.
Iodine: Why you can’t live without it
Iodine is a trace mineral which our thyroid glands need to synthesise the hormones, thyroxine, T4 and triiodothyronine, T3. These thyroid hormones affect virtually every cell in our body and are involved in almost all physiological processes as outlined below.
Functions of thyroid hormones
- Maintain the metabolic rate — the rate at which our body uses energy when at rest.
- Regulate our body temperature.
- Maintain a healthy body weight.
- Play a role in growth, development and cell repair.
- Maintain appropriate emotional responses.
- Maintain heart health (T3 is involved in regulating cholesterol levels and keeping the heart beat steady).
- Enhance the functions of insulin.
Iodine during pregnancy and lactation
Iodine plays a critical role in the development of the foetus’ brain and central nervous system. And if you’re breastfeeding, it remains essential that you get sufficient dietary iodine as your baby’s brain is still developing.
The thyroid hormone T4 is involved in myelination, the process during which a white fatty substance (the myelin sheath) forms around a nerve to enable faster nerve impulses, and hence, more efficient communication between the body cells and the brain. The thyroid hormones are also responsible for the proliferation of neurones.
Iodine deficiency: long term health consequences for your baby
Iodine deficiency – even a mild one – during pregnancy and breastfeeding puts the baby at risk of impaired brain development and a lowered IQ.
A severe deficiency of iodine during pregnancy or infancy could predispose the child to cretinism, a condition characterised by severe mental retardation, stunted growth, speech problems, deafness, spasticity and/or low levels of thyroid hormones.
Planning to conceive? Make sure you have adequate body iodine stores
“There’s growing evidence that what’s important is not just how much iodine you have during pregnancy, but how much you’ve had beforehand. If you go into pregnancy with long-standing iodine deficiency, you don’t have good supplies of it even though the thyroid can store quite a large amount and draw on it during pregnancy,” Sarah Bath, a nutrition researcher at the University of Surrey, told Advance, the magazine for Surrey postgraduates.
Sarah Bath also explained that gradually correcting any iodine deficiency before trying for a baby would protect the thyroid from a sudden shock — this could occur if you start taking supplements or rapidly increase your intake of iodine-rich foods when you were iodine-deficient.
Determining your iodine status
Because iodine content of food varies greatly, a dietary analysis of your diet intake would be inaccurate. Assessing your urinary iodine concentration is a more reliable method to measure your body stores of the mineral. Blood tests can also be carried out.
Iodine intake in the UK
You may be surprised to learn that studies suggest that the UK population may now be iodine-deficient. A UK-wide study investigating iodine deficiency among teenage girls found that 70% of young girls were iodine-deficient and another UK research revealed that 40% of pregnant women were iodine-deficient.
A little bit of history
Iodine deficiency was an acute worldwide problem until the 1920s when some countries decided to add iodine to common table salt. While the UK never really embraced the concept, it is fortunate that in the 1930s, farmers decided to add iodine to cattle feed for the health of their cows and to increase milk production — this increased the iodine content of milk.
However, in recent years, researchers have noted a decline in milk consumption and found that many of those who still drink milk are now looking for organic milk and dairy-products. To become organic-certified, many farmers decided to stop feeding their animals with iodine-fortified cattle feed and started using clover instead of artificial fertilisers. These two practices contributed to a decrease in the iodine content of milk — Sarah Bath reported that organic milk was 42% lower in iodine compared to conventional milk.
According to the Department of Health, adults need about 140mcg of iodine per day whereas the WHO and the US RDA recommend a slightly higher amount of 150mcg of the mineral per day.
There are no specific recommendations regarding iodine intake during pregnancy or breastfeeding in the UK but the WHO suggest that pregnant or breastfeeding mothers increase their intake to 250mcg per day. The US Institute of Medicine recommends a slightly lower intake of 220mcg per day during pregnancy and 290mcg if breastfeeding.
So, how much should you get? According to Sarah Bath, the UK iodine requirements for pregnancy are outdated: you should therefore try to aim to meet the amount set by the international bodies.
- Iodised salt — 1/4 teaspoon contains 76 mcg of iodine
- Conventional milk and dairy products
- Hens’ eggs
Who is at risk of iodine deficiency?
You’ve probably noticed than besides salt, iodine comes mostly from animal products — this means that vegans, vegetarians and anyone who avoids fish and/or dairy products because of allergies or intolerance would be at higher risks of iodine deficiency.
However, you can consider consuming more nuts, iodine-fortified breads and fruits and vegetables to increase your iodine intake.
Should an iodine supplement be considered?
This depends on your intake: if your diet is rich in iodine-rich foods, a supplement may not be warranted; talk to a registered dietitian if in doubt. Moreover, several prenatal multivitamins and mineral supplements contain iodine — check the label for ‘potassium iodide’.
Before taking any supplement, consult your GP first and if you do need supplements, make sure that they are in the form of ‘potassium iodide’ and do not contribute to more than 150µg of iodine per day.
Sarah Bath warns against the use of kelp supplements or seaweed — although kelp is rich in iodine, the amount of the mineral in those supplements can differ significantly from the amount printed on the label, thus providing excessive iodine.
Be careful: It is possible to get too much iodine
Consuming too much iodine during pregnancy or breastfeeding has been linked to mental and/or growth retardation as well as heart defects. That’s because the neonatal thyroid gland is still immature and more vulnerable to iodine induced hypothyroidism, a condition characterised by an abnormally underactive thyroid gland.
Just eat healthy
There’s no need to count all the micrograms of iodine you’re getting: simply follow the Eatwell Guide for a balanced dietary intake. A varied diet will also ensure that you’re getting sufficient nutrients to make the iodine in your diet more available for your thyroid.
Bath SC and Rayman MP (2013) Iodine deficiency in the U.K.: an overlooked cause of impaired neurodevelopment? Proc Nutr Soc. 72(2):226-35.
Bath et al (2010) Iodine deficiency in pregnant women living in the South-East of the UK. Proc Nutr Soc. doi:10.1017/S0029665110003460.
Vanderpump et al (2011) Iodine status of UK schoolgirls: a cross-sectional survey. Lancet. 377(9782):2007-2012.
Connelly et al (2012) Congenital hypothyroidism caused by excess prenatal maternal iodine ingestion. J Pediatr. 161(4):760-2.