The nutrient iodine has been under scrutiny over recent years, due to public health concern that 50% of UK women are at risk of iodine deficiency. Health consequences include thyroid dysfunction, goitre and poor mental function. Pregnant women are particularly at risk of iodine deficiency, and their unborn babies at increased risk of brain damage. The purpose of this blog is to highlight iodine deficiency as a real problem for pregnant women, provide guidance on dietary sources of iodine, suitable iodine supplementation and links to expert information via The UK Iodine Group.
Why is iodine deficiency so important?
Iodine is a constituent of thyroid hormones, essential for thyroid function and optimum functioning of the nervous system. Importantly, during early pregnancy iodine is essential for the healthy brain development of the foetus, and later in pregnancy provides iodine directly to the baby for maturation of the thyroid gland. Iodine deficiency during pregnancy is linked to brain damage; the more profound the deficiency, the more severe the health consequences for the developing foetus. This is a world-wide longstanding problem, and you can see a UK perspective the SACN statement on Iodine and Health published in 2014.
Dietary sources of iodine
Iodine comes from the soil, leaches into water and is naturally found in fish, shellfish and other seafood. Iodisation of salt was not adopted in the UK, as it was across the US, China, Asia and Europe throughout the 1920’s. In the UK it enters our food chain via dairy farming practice, as a constituent of sterilisers used in milking and of winter cattle feed. Together with encouraging children to drink more milk after WW2, cow’s milk is now the main dietary source of iodine in the UK. However our dietary practices are changing – we drink less cow’s milk, eat less fish and consume a more plant-based diet. As a result we are becoming iodine deficient. There are calls for iodisation, but as we have no consensus. Do have look at other dietary sources of iodine to check on your own intake.
Increased needs for iodine during pregnancy and breastfeeding
- Needs for iodine are 40% higher during pregnancy and breast-feeding
- There is a 50% surge of thyroid hormone production during the early part of pregnancy, mainly to supply iodine to the developing foetus. Mum’s daily needs for iodine are 200-250ug
- There are increased urinary losses during pregnancy
- Iodine is required by the unborn baby from around 20 weeks gestation, to support the start of thyroid function; drawing this from maternal iodine supplies
- Once born babies daily needs for iodine throughout the first year are 50-60ug and breast milk contains around 7ug/100mls (formula contains 12-14ug/100mls)
Taking an iodine supplement
Breast feeding mums are at further risk of iodine deficiency if following a milk free diet for their cow’s milk allergy baby. It is important to be aware that the nutritional composition of milk alternatives is poor, usually without iodine and sometimes even without calcium! Do take a supplement if you cannot get enough iodine from dietary sources, bearing in mind that single supplements of iodine are not routinely available (partly because too much is dangerous). Pregnant women should not take kelp or seaweed supplements for this reason. Multivitamin & mineral supplements now routinely contain iodine, providing around 150ug, which is the usual daily adult need. The rest can more easily be found in the diet.